Unit-3_Physics_Chemistry_Biology - New Indian Model School, Dubai

CBSE-iScience• Physics Electromagnetic Induction• Chem Electricity and Chemistry• Biology How Do Organisms Reproduce?CLASSXUNIT-3Shiksha Kendra, 2, Community Centre, Preet Vihar,Delhi-110 092 India

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PREFACEThe Curriculum initiated by Central Board of Secondary Education -International (CBSE-i) is a progressive step in makingthe educational content and methodology more sensitive and responsive to the global needs. It signifies the emergence of afresh thought process in imparting a curriculum which would restore the independence of the learner to pursue thelearning process in harmony with the existing personal, social and cultural ethos.The Central Board of Secondary Education has been providing support to the academic needs of the learners worldwide. Ithas about 11500 schools affiliated to it and over 158 schools situated in more than 23 countries. The Board has always beenconscious of the varying needs of the learners in countries abroad and has been working towards contextualizing certainelements of the learning process to the physical, geographical, social and cultural environment in which they are engaged.The International Curriculum being designed by CBSE-i, has been visualized and developed with these requirements inview.The nucleus of the entire process of constructing the curricular structure is the learner. The objective of the curriculum is tonurture the independence of the learner, given the fact that every learner is unique. The learner has to understand,appreciate, protect and build on values, beliefs and traditional wisdom, make the necessary modifications, improvisationsand additions wherever and whenever necessary.The recent scientific and technological advances have thrown open the gateways of knowledge at an astonishing pace. Thespeed and methods of assimilating knowledge have put forth many challenges to the educators, forcing them to rethinktheir approaches for knowledge processing by their learners. In this context, it has become imperative for them toincorporate those skills which will enable the young learners to become 'life long learners'. The ability to stay current, toupgrade skills with emerging technologies, to understand the nuances involved in change management and the relevantlife skills have to be a part of the learning domains of the global learners. The CBSE-i curriculum has taken cognizance ofthese requirements.The CBSE-i aims to carry forward the basic strength of the Indian system of education while promoting critical and creativethinking skills, effective communication skills, interpersonal and collaborative skills along with information and mediaskills. There is an inbuilt flexibility in the curriculum, as it provides a foundation and an extension curriculum, in all subjectareas to cater to the different pace of learners.The CBSE has introduced the CBSE-i curriculum in schools affiliated to CBSE at the international level in 2010 and is nowintroducing it to other affiliated schools who meet the requirements for introducing this curriculum. The focus of CBSE-i isto ensure that the learner is stress-free and committed to active learning. The learner would be evaluated on a continuousand comprehensive basis consequent to the mutual interactions between the teacher and the learner. There are some nonevaluativecomponents in the curriculum which would be commented upon by the teachers and the school. The objective ofthis part or the core of the curriculum is to scaffold the learning experiences and to relate tacit knowledge with formalknowledge. This would involve trans-disciplinary linkages that would form the core of the learning process. Perspectives,SEWA (Social Empowerment through Work and Action), Life Skills and Research would be the constituents of this 'Core'.The Core skills are the most significant aspects of a learner's holistic growth and learning curve.The International Curriculum has been designed keeping in view the foundations of the National Curricular Framework(NCF 2005) NCERT and the experience gathered by the Board over the last seven decades in imparting effective learning tomillions of learners, many of whom are now global citizens.The Board does not interpret this development as an alternative to other curricula existing at the international level, but asan exercise in providing the much needed Indian leadership for global education at the school level. The InternationalCurriculum would evolve on its own, building on learning experiences inside the classroom over a period of time. TheBoard while addressing the issues of empowerment with the help of the schools' administering this system stronglyrecommends that practicing teachers become skillful learners on their own and also transfer their learning experiences totheir peers through the interactive platforms provided by the Board.I profusely thank Shri G. Balasubramanian, former Director (Academics), CBSE, Ms. Abha Adams and her team and Dr.Sadhana Parashar, Head (Innovations and Research) CBSE along with other Education Officers involved in thedevelopment and implementation of this material.The CBSE-i website has already started enabling all stakeholders to participate in this initiative through the discussionforums provided on the portal. Any further suggestions are welcome.Vineet JoshiChairman

ACKNOWLEDGEMENTSAdvisoryConceptual FrameworkShri Vineet Joshi, Chairman, CBSEShri G. Balasubramanian, Former Director (Acad), CBSEShri N. Nagaraju, Director(Academic), CBSEMs. Abha Adams, Consultant, Step-by-Step School, NoidaDr. Sadhana Parashar, Director (Training),CBSEIdeatorsMs. Aditi Misra Ms. Anuradha Sen Ms. Jaishree Srivastava Dr. Rajesh HassijaMs. Amita Mishra Ms. Archana Sagar Dr. Kamla Menon Ms. Rupa ChakravartyMs. Anita Sharma Ms. Geeta Varshney Dr. Meena Dhami Ms. Sarita ManujaMs. Anita Makkar Ms. Guneet Ohri Ms. Neelima Sharma Ms. Himani AsijaDr. Anju Srivastava Dr. Indu Khetrapal Dr. N. K. Sehgal Dr. Uma ChaudhryEnglish :Ms. Sarita ManujaMs. Renu AnandMs. Gayatri KhannaMs. P. RajeshwaryMs. Neha SharmaMs. Sarabjit KaurMs. Ruchika SachdevGeography:Ms. Deepa KapoorMs. Bharti DaveMs. BhagirathiMs. Archana SagarMs. Manjari RattanEnglish :Ms. Rachna PanditMs. Neha SharmaMs. Sonia JainMs. Dipinder KaurMs. Sarita AhujaMaterial Production Group: Classes I-VDr. Indu Khetarpal Ms. Rupa Chakravarty Ms. Anita Makkar Ms. Nandita MathurMs. Vandana Kumar Ms. Anuradha Mathur Ms. Kalpana Mattoo Ms. Seema ChowdharyMs. Anju Chauhan Ms. Savinder Kaur Rooprai Ms. Monika Thakur Ms. Ruba ChakarvartyMs. Deepti Verma Ms. Seema Choudhary Mr. Bijo Thomas Ms. Mahua BhattacharyaMs. Ritu BatraMs. Kalyani VoletiCoordinators:Dr. Sadhana Parashar, Ms. Sugandh Sharma, Dr. Srijata Das, Dr. Rashmi Sethi,Head (I and R) E O (Com) E O (Maths) O (Science)Shri R. P. Sharma, Consultant Ms. Ritu Narang, RO (Innovation) Ms. Sindhu Saxena, R O (Tech) Shri Al Hilal Ahmed, AEOMs. Seema Lakra, S OMathematics :Dr. K.P. ChindaMr. J.C. NijhawanMs. Rashmi KathuriaMs. Reemu VermaPolitical Science:Ms. Sharmila BakshiMs. Archana SoniMs. SrilekhaScience :Dr. Meena DhamiMr. Saroj KumarMaterial Production Groups: Classes IX-XMs. Rashmi RamsinghaneyMs. Seema kapoorMs. Priyanka SenDr. Kavita KhannaMs. Keya GuptaMs. Preeti Hans, Proof ReaderScience :Ms. Charu MainiMs. S. AnjumMs. Meenambika MenonMs. Novita ChopraMs. Neeta RastogiMs. Pooja SareenEconomics:Ms. Mridula PantMr. Pankaj BhanwaniMs. Ambica GulatiMaterial Production Groups: Classes VI-VIIIMathematics :Ms. Seema RawatMs. N. VidyaMs. Mamta GoyalMs. Chhavi RahejaPolitical Science:Ms. Kanu ChopraMs. Shilpi AnandHistory :Ms. Jayshree SrivastavaMs. M. BoseMs. A. VenkatachalamMs. Smita BhattacharyaGeography:Ms. Suparna SharmaMs. Leela GrewalHistory :Ms. Leeza DuttaMs. Kalpana Pant

ContentPhysicsSyllabus Coverage 1Electromagnetic Induction• Core And ExtensionMatrix 2Scope Document 4• Learning Objectives• Cross Curricular Links• Suggested ActivitiesTeachers' Notes (TN) 5Teacher - Student Support Material (TSSM) 17Formative AssessmentRubrics of Assessment- Physics 47Suggested Videos And Resources 47Syllabus Coverage 48Electricity and Chemistry• Core and ExtensionMatrix 49Scope Document 53Teachers' Notes (TN) 54Extra Reading, Activities and Question Bank for theTeacher -ChemistryTeacher - Student Support Material (TSSM) -Chemistry 63Formative Assessment –ChemistryCHEMISTRYRubrics of Assessment- Chemistry 111Suggested Videos and Resources 113

BIOLOGYSyllabus Coverage 114Howdo Organisms Reproduce?• Learning Objectives• Cross Curricular Links• Suggested ActivitiesMatrix 115Scope Document 120Teacher Note (TN) 122Teacher - Student Support Material (TSSM) - Biology 136Formative Assessment – BiologyRubrics of Assessment- Biology 227Suggested Videos and Resources 228

SYLLABUS COVERAGEUnit 3 – ELECTROMAGNETIC INDUCTIONSYLLABUSCoreElectromagnetic InductionFleming‘s Right Hand ruleFactors affecting the magnitude of induced currentFunction and working of the generatorWorking of transformerAlternating currentTransmission of electric power at high voltagesUnits used to measure electric power consumption1

MATRIXCONTENT/CONCEPT INTENDED LEARNING SKILLElectromagnetic Induction andFaraday‘s Lawshttp://www.phy.hk/wiki/englishhtm/Induction.htmTo familiarize the students withthe phenomenon ofelectromagnetic induction andthe laws governing it.Understand andanalysehttp://www.metacafe.com/watch/601268/faradays_law_of_induction/Fleming‘s Right Hand ruleFunction and working of theelectric generatorUse PPT – Magnetic effects ofcurrent and video clips in thefollowing linkshttp://www.animations.physics.unsw.edu.au//jw/electricmotors.html#generatorshttp://home.acity.de/walter.fendt/physengl/generatorengl.htmStudents will be able to stateFleming‘s Right Hand Rule andfind out the direction of theinduced current when thedirections of the magnetic fieldand motion are known.Student will understand theconstruction and working of adynamo, with the help ofillustrations, classdemonstrations and java applet.Observation, use ofvocabularyIdentification,Application,learning by doing.Understanding,Application,Observation,learning by doing2

Mutual inductance andworking of transformerAlternating currentExplain using video cliphttp://www.youtube.com/watch?feature=player_embedded&v=HqMqdFNWX4s#at=242Transmission of electric powerand (the commercial) units usedto measure electric powerconsumption.Students will understand thephenomenon of inducingcurrent through mutualinductance and apply it tounderstand the working of atransformer.Student will be able tounderstand and explain themeaning of alternating current,and its difference from a directcurrent.To make the students aware ofthe advantages of use ofalternating current for longdistance transmission and tomake them appreciate the needand advantages of savingelectricity as far as possible.Application,Learning by doing,observation,appreciation ofcontribution ofteam work inscience.Reasoning andanalytical skillsObservation,Estimation,accuracymeasurement andnumericalproblem solvingskills3

Intended Learning outcomesScope DocumentAt the end of this unit, students should be able toDescribe the phenomenon of Electromagnetic inductionState , explain and apply Fleming‘s right hand ruleDescribe and understand the factors affecting the current induced in a conductorplaced in a (changing) magnetic field.Describe and understand the function and working of a generatorDescribe the working of a transformer.Describe alternating currentUnderstand and appreciate the importance of transmission of electric power athigh voltages.Understand the units used to measure electric powerand to do relevantnumerical calculations.Cross curricular linksMathematics – Calculating electricity bill of electric energy used for domestic/commercial purposesICT – Using and preparing power point presentations and videosApplied Physics – Construction and working of devices like generators andtransformersEnergy Transformation- The role of different types of energy sources—thermal,hydroelectric kinetic & potential energy, nuclear energy and solar energy---- inlarge scale generation of electric energy.4

Teacher’s Notes (TN)Electricity forms an exciting field of study of human creativity and excellence for use ofscientific principles in the service of human kind. Though the students might have gotacquainted with common terms related to electricity in lower classes, the presentchapter on Electromagnetic. Induction in grade X focuses on helping them clearlyunderstand the underlying fundamental phenomenon responsible for generation ofelectricity and the working of few electrical devices. After studying this unit, the learnerwill be able to:define the term ‗Electromagnetic induction‘State the laws of ‗Electromagnetic induction‘Apply laws of electromagnetic induction to know direction of induced current ina given situation.Understand and explain the principle, construction and working of analternating current generator as well as direct current generator.Distinguish between alternating current and direct current.Understand and explain the principle, construction and working of atransformer.Appreciate the use of a transformer for long range transmission of electricalenergy.Carry out simple activities based on alternating current.IntroductionThe teaching of the phenomenon of electromagnetic induction provides the teacherwith an interesting and unique opportunity of emphasizing the role, impact andimportance of scientific discoveries and inventions on the social and cultural life of thehuman society as a whole. It has been aptly said:5

―Had there been no Faraday, there would have been no Electricity.‖It is important for the teacher to convey that the significance of the word FARADAY inthis statement is not on Faraday, the man, but on the very important discovery of thephenomenon of Electromagnetic Induction, made by him. All large scale production ofelectricity, in our present day world is through this phenomenon. The impact ofavailability of electricity, to one and all, on the human society, is there for all of us to seeand appreciate.The topic may be introduced by using imaginative and interesting questions like: Hadelectricity not been discovered by Faraday, what difference would it have made tohuman civilization? Imagine there is no electricity in your city for a month, how will itaffect you lifestyle? Why is it not possible to light an ordinary domestic electric lamp byusing dry cells or a battery? The purpose of asking such questions is to provokethinking of the learners. Sometime may be kept aside for listening to their responsesand reflecting why they think so. Effort may be made to involve those learners to speakwho are usually quiet and lack confidence to interact in the classroom.In order to acquaint the learners with few other terms and topics which have beenincluded in this unit, you may use few more questions to stimulate curiosity. Have youever seen a dynamo or a transformer? What is its function in electrical circuits? Haveyou ever seen or designed or used a cycle dynamo? What kind of energytransformations take place in it? The list of such real life related and interestingquestions can be large. Keep such question handy to connect classroom learning to lifeoutside the school.Providing concrete experiencesLearners learn best when concrete experiences are provided to explain related concepts.Activity I included in teacher-student support material in the unit may be demonstratedto show how electric current can be generated by moving a strong magnet into a copper6

coil or moving a coil in a magnetic field. Care may be taken to ensure that the deflectionobserved in the detecting instrument is appreciable and and can be seen easily. It isadvisable to use a microammeter or a galvanometer for this purpose. Students may beinvolved to perform the activity themselves. The meaning of terms electromagnetic,induction, induced emf, induced current etc. may be clearly explained. Followingquestions can be of great help to understand the factors affecting the magnitude ofinduced currentWhat do you expect to observe if a stronger magnet is used in thedemonstration?What is likely to be observed if the magnet or the coil is moved with greaterspeed?Why does the micrometer show deflection only when the magnet or the coil ismoved and not otherwise?Why do you observe deflection in opposite directions when the direction ofmovement of the magnet is reversed?What exactly is the source of electric energy being generated?The questions may be followed by carrying out different activities to get answers toabove questions in order to help them arrive at Faraday‘s laws of Electromagneticinduction. These laws may then be clearly stated. The concepts taught so far may bestrengthened by summerising and stating the key learning points in clear terms.The fact that the direction of induced current in certain situations can be determined byapplying a simple rule called Fleming‘s Right hand Rule can be explained to thelearners by using a visual-say a chart showing the diagram of a right hand, clearlyindicating the direction of magnetic field, the direction of motion of the conductor in themagnetic field and direction of inducted current being produced in the conductor. Thelearners may be helped to remember that Forefinger stands for magnetic Field., thumbstands for Motion of the conductor and Central finger stands for Current induced in the7

conductor (F for Field and Forefinger, M for Motion and thuMb and C for Central &Current may be repeated). One or two students may be involved to verify it from thediagram used for this purpose and by stretching the right hand. In order to help thelearners internalize the concept, questions may be asked as to what will happen whenthe direction of magnetic field, the direction of Motion of the conductor or both arechanged. It is also very essential to emphasise the difference between situations relatedto use of Fleming’s Right Hand Rule and Fleming’s Left Hand Rule. When do we useFleming‘s Right Hand Rule or Fleming‘s Left Hand Rule need to be made very clear inorder to remove confusion in their minds.Demonstration: The working principle of an electric generator can be best explained byusing a model of a simple dynamo which is easily available and should be kept readyfor this purpose. Different parts of an electric generator and the role of its every part beclearly explained using the model. Activity -3 included in Student- Teacher material inthis unit may be demonstrated and the reason for generation of electric current beexplained. A chart or a visual can be an added advantage. The energy conversions in anelectric generator may be brought out clearly.The learners may be asked to give examples of different kinds of commercial electricgenerators they might have heard of. Clues may be provided for use of differentfuels/resources which are used for conversion into electric energy in differentcommercial electric generators. You may frame questions to either stimulate curiosity orelicite correct responses related to different kinds of energy conversions taking place inHydro-electric generator, Thermal Power generator or a Nuclear power generators. Thelearners may also be suggested to visit any of the commercial electric generator, ongetting an opportunity.8

Learners‘ observational skills and reasoning ability can be used to explain the differentbetween a.c. and d.c. You can show a dry cell or a battery (accumulator) and ask themto carefully observe ‗+‘ and ‗-‘ markings on it. Following questions can be of immensehelp to make the learners internalize the difference between a.c. and d.c.(i)(ii)Why is a dry cell or a battery marked ‗+‘ and ‗- ‘and what does it indicate?Why any electric point in our domestic electrical fittings where we connect ourappliances is not marked ‗+‘ or ‗-‘ ? What does is indicate?(iii) What does d.c. stand for and what does it mean?(iv) What does a.c. stand for and what does it mean?(v)What does frequency of a.c. mean?(vi) What is the frequency of d.c.?The responses to above questions may be summed up or corrected to explain the exactdifference between alternatively current (a.c.) and direct current (d.c.). The terms suchas alternating, direct, generator, frequency may be clearly explained. Another importantdifference related to continuous variation of magnitude of current In case of alternatingcurrent and the constant magnitude of current in case of direct current be highlightedby using graphical representation of the two, explaining. Another important differencerelated to continuous variation of magnitude of current in case of alternating currentand the constant magnitude of current in case of direct current be highlighted by usinggraphical representation of the two, explaining clearly the physical significance of thesketches (waveform for a.c. and straight line for d.c.)DemonstrationModels of a.c. generator and d.c. generator may be kept handy of show the differencebetween the construction of the two. The important role of slip rings in a.c. generator9

and split rings in d.c. generator which affects the direction of flow of current beexplained. Use of a chart showing the diagrams of a.c. and d.c. generators and thedirection of electric current in the armature and the external circuit for differentorientations of the coil in two generators can add value to clarity of concepts to thestudents. The understanding of the principle, construction and working of the generatorcan be ascertained and reinforced by asking pinpointed questions kept ready for thispurpose.Activity 6 included in Teacher-student support material may be demonstrated to showand introduce the phenomenon of mutual induction. Involving students in makingdemonstration can promote their interest and arouse curiosity. The factors affecting themagnitude of current induced in the secondary (Second coil) may be explained in anindirect manner by asking the following questions:How will induced current in the secondary coil be affected by changing thedistance between the coils?How will the same observation be affected by increasing the number of turns inthe two coils?How will the induced current in the secondary coil change by changing themedium between the coils?What difference in observation will be made if the orientation of the two coils ischanged?What will you observe if the first coil (primary coil) is connected to a source ofdirect current?Correct explanation may then be provided for the above questions along withcorresponding changes in demonstration (Whatever practically possible) to enable thelearners to understand the phenomenon of mutual induction.10

The explanation of phenomenon of mutual induction may be extended to theprinciple and working of a transformer. For this purpose, model of a transformer maybe shown to the students to explain its parts and function of different parts. The use ofchart for explaining the construction and working of a transformer can be of immensehelp.In order to help the learners connect classroom learning to real life situation, theymay be asked whether they have ever seen such a device supported on electric polesand the role of such a device. They may be provided adequate explanation for the useof transformer in electrical circuits. The difference between a step-up-transformer and astep-down transformer alongwith the desired changes in their designs may also beexplained. The need and use of a step-up transformer for long range transmission ofenergy may be clarified by making the learners do mathematical calculations for loss ofelectrical energy during transmission. Suitable data may be provided for makingrelevant calculations to clarify the concept of losses when the electrical energy istransmitted at ordinary voltage, hence highlighting the use of a step-up transformer atthe generating station and a step-down transformer at the receiving station. Activity 7included in teacher-learner support material may be carried out to strengthen therelated concept.The teaching-learning of complete unit, thus, requires and demands number ofdemonstrations, hands-on-activities, use of visual aids and models for effectivetransaction of the content. Teaching can be made more effective and enjoying byshowing video clippings of electrical devices and their use in daily life. Additional useof web-links and other electronic resources can further enrich the quality of learning.The unit also expects linking the concepts being taught in the classroom to everyday lifeapplications. Asking probing questions at every step can help the learners acquire indepthunderstanding of the concepts leading to their enhanced interest in the topic forself-learning and extended learning.11

The teacher would go through the links, video clips and PPT prior to teaching in theclass. She is expected to frame thought provoking questions based on the web links1. To explain EMI and Faraday‘s Laws, teacher can make use of the following videoclipshttp://www.phy.hk/wiki/englishhtm/Induction.htmhttp://www.metacafe.com/watch/601268/faradays_law_of_induction/2. Teacher can explain the reasons for the observations of Activity 2 to the students inthe following mannerAs the magnet falls, the magnetic field around it constantly changes position. As themagnet passes through a given portion of the metal tube, this portion of the tubeexperiences a changing magnetic field, which induces the flow of induced currents(called eddy currents) in an electrical conductor, such as the copper or aluminumtubing. The eddy currents create a magnetic field that exerts a force on the fallingmagnet. The force opposes the magnet's fall. As a result of this opposing (magnetic)force, the magnet falls much more slowlyEddy currents are often generated in transformers and lead to power losses. Tominimize their effects, thin, laminated strips of metal are used in the construction ofthe cores of power transformers, rather than making these cores out of one solidpiece of metal. The thin strips are separated by insulating layers. As a result, theeddy currents get confined to the strips and are very much reduced. This reductionof eddy currents, results in a very significant reduction in the power losses.Eddy currents are also used to dampen unwanted oscillations in many mechanicalbalances. Examine your school's balances to see whether they have a thin metal stripthat moves between two magnets.12

3. You might introduce Activity 3 by saying:A dynamo or generator is a carefully-designed piece of equipment. There is a coil of wire anda magnetic field. There is motion. Electricity (a voltage) is generated. You can understandthe principle of the dynamo by starting with a simpler situation: you have a coil and amagnet, and you introduce a relative motion between them. What will you discover?The students would find out that:• the current flows only when the magnet and the coil are moving relative to eachother;• the current changes direction when the magnet is inserted into the coil and thenremoved from the coil;• more turns on the coil produce bigger currents provided the total resistance ofthe wire remains the same;• the faster the magnet is moved, the greater is the maximum deflection in thedetecting device (say, a moving coil galvanometer).You can Refer to the following siteshttp://www.animations.physics.unsw.edu.au//jw/electricmotors.html#generatorshttp://home.a-city.de/walter.fendt/physengl/generatorengl.htm(java applet for working of generator)4. Teacher must remember the following points in order to perform Activity 4 in theclassroom• Turning a motor by hand makes the motor into a dynamo. The resulting(induced) potential difference can be measured on a sensitive galvanometer.13

Frequently it is enough just to use a sensitive ammeter, as long as confusion doesnot arise. The dynamo effect produces an emf (a potential difference), and not acurrent.• Students should note that turning the motor faster produces a greater deflectionof the meter. Reversing the spin of the motor generates a deflection in theopposite direction.• The wave form of the output of this dynamo can be observed on a C.R.O. It willnot be a 'flat graph' but would show the changes in magnitude of the emfthroughout the cycle. However, it will be uni-directional. If either brush fails tomake a connection as it rotates, there will be a considerable AC potentialdifference between the input terminals of the C.R.O. This will cause a misleadingtrace of AC mains on the tube. Connecting a 10 kW resistor across the inputterminals of the C.R.O. will prevent this.• If you use a home-made model electric motor which has run for an appreciabletime, the brushes and commutator can be dirty and may have a high resistance.Strip down and scrape the brushes and commutator with emery-paper to cleanthem. Avoid finger grease. Taking these precautions may increase thegalvanometer deflection several times.• AC version: As an alternative to the slip rings, it is possible to make a temporarydynamo that will work for a few turns. Bring out a pair of leads of thin wire fromthe coil, and let the leads twist up as the coil is turned.• The AC wave form produced by the dynamo is best seen by connecting thedynamo to a C.R.O. The trace should resemble the traditional sine wave.5. Teacher can use the following video clipping to make the student understand thedifference between A.C and D.C14

http://www.youtube.com/watch?feature=player_embedded&v=HqMqdFNWX4s#at=2426. Following teaching tips are to be kept in mind while performing Activity 6• Power lines connect power stations to the consumer. This is convenient, but thereis a cost to pay in energy terms. An electric current warms up the transmissioncables and so there are 'energy losses' as the atmosphere is warmed up.In this model version, the wire used has significant resistance so that 1.5 mrepresents many km of transmission line. It is clear that energy is 'lost' along thetransmission wires so much so that the 'village' at the end of the transmissionwires receives very little energy from the 'power station' at the other end of thewire.• As well as measuring voltages, an ammeter (reading to at least 2 ampere) can beconnected into the supply line. Students can check that the current remains thesame around the power line circuit; the current to the 'power station' lamp isgreater than that to the 'village' lamp.• In order to understand what is happening, students need some quantitativeideas about electricity. A current of 5 amps means a flow of charge of 5 coulombsper second. A voltmeter measures the energy. A potential difference of 3 voltsbetween any two points, means that 3 joules of energy are given to each coulombof charge in being transported from the first to the second point.• Thus a volt is defined as a joule/coulomb and an ampere (amp for short) isdefined as a coulomb of charge flowing per second. So with V volts and Qcoulombs, the energy transferred is V x Q joules. The current is I = Q/time, and sothe energy transferred is V x I joules per second or VXI watt. (A joule per secondis also known as a watt, which is a measure of power.)15

• By measuring the current and potential difference at the power station end of the line,and at the village end, you can calculate the 'power loss' along the line. The potentialdifference measured across one wire, multiplied by the current in the wire, will give thepower loss of one wire, and so the total power loss of the wires is twice as much. This isa check on the previous calculation. The input energy should now be equal to the energytransferred to the output plus the energy transferred to warming up the transmissionwires.• The heating effect of a current is proportional to the square of the current. This meansthat high currents and low potential differences warm up the wires more than lowcurrents and high potential differences. Therefore, the cables transfer more energy to theenvironment than to the village in the high current case. Another way of reducing lowerpower losses is to reduce the resistance of the transmission lines. This is done by usingwires of low resistivity such as copper or aluminium. (Silver has an even lowerresistivity but it would be very expensive!) Increasing the diameter of the cable woulduse more copper or aluminium and that would be expensive, and they would also beheavier and so need more support. The efficiency of the system can be calculated from:efficiency = power taken by the village/power supplied at the power stationTeacher can use the given link to further strengthen the conceptswww.practicalphysics.org/go/Collection16

TEACHERSTUDENTSUPPORTMATERIAL17

ELECTROMAGNETIC INDUCTIONWe have already studied in the previous chapter that, if electrical current is flowing in aconductor, there is an associated magnetic field created around the wire. In this chapterwe will study its reverse phenomenon: that is, if we move a wire inside a magnetic field(in a proper way), an electrical current can get generated in the wire.Warm up ActivityActivity 1Learning outcomesExplain how current can be induced in a conductor without making contact.Describe the process of induction.Material required; piece of conducting wire wound around an iron bar, ammeter and astrong horse shoe magnet.Method; Connections are made as shown in the figure. Teacher demonstrates howammeter readings change, when horse shoe magnet is moved around the coil.18

Experiment should be repeated byMoving the magnet fasterUsing a stronger magnetIncreasing the length of the wireMoving the coil fasterCurrent is produced in a conductor when it is moved through a magnetic field, becausethe magnetic field is applying a force on the free electrons in the conductor and causingthem to move. This process of generating current in a conductor, by placing theconductor in a changing magnetic field, is called induction. This is called inductionbecause there is no physical connection between the conductor and the magnet. Thecurrent is said to be induced in the conductor by the magnetic field.One basic requirement for this electromagnetic induction to take place is that theconductor, (which is often a coil or a piece of wire), must have its plane/ lengthperpendicular to the magnetic field lines. This is needed in order to produce themaximum force on the free electrons. The direction that the induced current flows isdetermined by the direction of these field lines and by the direction the wire is movingin the field. In the figure above the ammeter (the instrument used to measure current)indicates when there is a current in the conductor.Faraday’s Laws of Electromagnetic inductionWhile Oersted‘s surprising discovery ,of getting magnetism from electric currents,paved the way for more practical applications of electricity, it was Michael Faraday whogave us the key to the practical generation of electricity: electromagnetic induction.Faraday discovered that a voltage would be generated across a length of wire if thatwire was exposed to a perpendicular magnetic field flux of changing intensity.19

An easy way to create a magnetic field of changing intensity is to move a permanentmagnet next to a wire or coil of wire. Remember: the magnetic field must increase ordecrease in intensity perpendicular to the wire (so that the magnetic field lines "cutacross" the conductor), or else no voltage, (or a very much reduced voltage), will beinduced:Faraday was able tomathematically relate the rateof change of the magnetic fieldlines (magnetic flux) withinduced voltage. He was ableto show that the instantaneousinduced voltage, or the inducedvoltage at a specific point intime, equals the time rate ofchange (change per unit time)of the magnetic field lines(magnetic flux) linked with thecoil at that instant of time.We write it in the mathematical form:20

The "d/dt" term is standard calculus notation, representing rate-of-change of flux overtime. "N" stands for the number of turns, or wraps, in the wire coil (assuming that thewire is formed in the shape of a coil for maximum electromagnetic efficiency).This phenomenon is put into obvious practical use in the construction of electricalgenerators, which use mechanical power to move coils of wire across a magnetic field togenerate voltage. However, this is by no means the only practical use for this principle.If we recall that the magnetic field produced by a current-carrying wire was alwaysperpendicular to that wire, and its magnitude varied with the amount of currentthrough it, we can see that a wire is capable of inducing a voltage along its own lengthsimply due to a change in current through it. This effect is called self-induction: achanging magnetic field produced by changes in current through a wire inducingvoltage along the length of that same wire. If the magnetic field flux is enhanced bybending the wire into the shape of a coil, and/or wrapping that coil around a materialof high permeability, this effect of self-induced voltage will be more intense.REVIEW:• A magnetic field of changing intensity perpendicular to a wire will induce avoltage along the length of that wire. The amount of voltage induced dependson the rate of change of the magnetic field flux and the number of turns ofwire (if coiled) exposed to the change in flux.• Faraday's equation for induced voltage: e = N(dΦ/dt)• A current-carrying wire will experience an induced voltage along its length ifthe current changes (thus changing the magnetic field flux perpendicular tothe wire, thus inducing voltage according to Faraday's formula).21

Fleming's Right hand RuleFleming's right hand rule (for generators) shows the direction of induced current flowwhen a conductor moves in a magnetic field.The right hand is held with the thumb, first finger and second finger mutually at rightangles, as shown in the diagram.The Thumb represents the direction ofMotion of the conductor. The First finger represents thedirection of the Magnetic Field.The Second finger represents thedirection of the induced or generatedCurrent (in the classical direction, i.e,from positive to negative).Factors affecting the magnitude of the Induced Current in a magnetic fieldWe have noted above that we can get an induced current in a conductor placed in amagnetic field .The magnitude of the induced current, however depends upon certainfactors .First of all conductor needs to be present in the magnetic field .The change in themagnetic field associated with the conductor ,can however come about either throughchange in the strength of the magnetic field itself or through a change in the position ofthe conductor in the magnetic field.The rate of change of the magnetic field associated with the conductor plays a centralrole in the magnitude of the induced current.22

The more is this rate of change of (through same same change in the magnetic field in ashorter time interval or through a larger change in the magnetic field in the same timeinterval) the more is the strength of the induced current.The orientation of the conductor with respect to (changing ) magnetic field , also plays arole. When the conductor is placed normal to the (changing )magnetic field ,the inducedcurrent increases its magnitude .There would be no induced current (even in a changingmagnetic field ) if the magnetic field lines graze the conductor and do not cut through it.When we are considering the induced current in one coil ,due to a change in current in aneighboring coil the number of turns in each of the two coils also affect the inducedcurrent .More the no. of turns ,more is the induced current .In fact it is the product ofthe no. turns in the two coils ,that would affect the strength of the induced current inthe second coil.In this case of the two coils, the nature of the medium between them also plays a role.With a ferromagnetic material (like iron), we would get a greater induced current thanwhat we get with air as the medium between them.The induced current, in case of two coils, would also depend on their distance ofseparation. The closer are the two coils to each other, the more is the induced current(keeping all other conditions the same). One important fact has to be kept in mind.The induced effect, associated with a changing magnetic field is always an inducedE.M.F. We get an induced current only when the second coil is a closed coil. This is justa reassertion of the well known fact that a source of E.M.F can send a current only whenthe circuit is closed.So remember this: we can talk of induced currents but they are there only when thecircuit is closed. The induced quantity, whenever it can appear, is always an inducedemf. It can give rise to an induced current only when the circuit is closed.23

Activity 2Application of EMILearning objectives; Students will understand why a magnet falls more slowly througha metallic tube than it does through a nonmetallic tube.Material RequiredA strong magnet bar preferably a neodymium magnet.A nonmagnetic object, such as a pen or a pencil.One (about 1m) length of aluminum, copper, or brass tubing (do not use iron!)with an inner diameter larger than the magnet and with walls as thick aspossible.One (about 1m) PVC or other nonmetallic tubing.Optional: 2 thick, flat pieces of aluminum (available at hardware and homerepairstores); cardboard; masking tape; rubber bands or cord.MethodHold the metal tube vertically. Drop the magnet through the tube. Then drop anonmagnetic object, such as a pen or pencil, through the tube. Notice that the magnettakes noticeably more time to fall. Now try dropping both magnetic and nonmagneticobjects through the PVC tube.In addition to dropping these objects through the tubes, a very simple, visible, anddramatic demonstration can be done by merely dropping the magnet between twothick, flat pieces of aluminum. The aluminum pieces should be spaced just slightlyfarther apart than the thickness of the magnet. A permanent spacer can easily be madewith cardboard and masking tape if you don't want to hold the pieces apart each time.Rubber bands or cord can hold the pieces all together. The flat surfaces need to be onlyslightly wider than the width of the magnet itself. Thickness, however, is important.The effect will be seen even with at least 2.5 cm thick pieces of aluminum and aminimum of 15 cm fall.24

Procedurea Wind the copper wire on the ferromagnetic rod to form a cylinder with theferromagnetic rod as axis. Leave 0.5 cm of wire on either side of the rod. Thiswould form the so called ‗test coil‘.b. Remove the insulation from the two ends of the copper wire and connect an LEDin series.c. Connect the primary coil of the demountable transformer to the AC mains.d. Hold the test coil (ferromagnetic rod with copper wire) in your hand and move thetest coil close to the secondary coil, preferably along its axis. (A circular inductorcoil will have its magnetic field along its axis.) The LED glows.e. If the primary coil is changed for a smaller one, connected to the 20 V DC, the LEDglows as the test coil is moved towards or away from the secondary coil.Electromagnetic Induction – In-Class Worksheet 1Demo 1A strong ―bar‖ magnet is made by joining many button magnets. This magnet isinserted into and subsequently removed from a solenoid. Note the approximate sizeand direction of deflection on the galvanometer when the magnet is:a. Going in: ___________________b. Stationary inside the solenoid: ______________________c. Coming out: _________________26

Demo 2A weaker magnet is used this time by using less button magnets. The solenoid is thesame as in Demo 1. Note the approximate size and direction of deflection on thegalvanometer when the magnet is:a. Going in: ___________________b. Stationary inside the solenoid: ______________________c. Coming out: _________________Demo 3Using the same magnet and solenoid as in Demo 1, the magnet is now inserted andremoved at a slower speed. Note the approximate size and direction of deflection on thegalvanometer when the magnet is:a. Going in: ___________________b. Stationary inside the solenoid: ______________________c. Coming out: _________________Demo 4A home-made solenoid with many less turns of wire than the solenoid is used this timewith the same magnet as in Demo 1. Note the approximate size and direction ofdeflection on the galvanometer when the magnet is:a. Going in: ___________________b. Stationary inside the solenoid: ______________________c. Coming out: _________________27

ConclusionFrom your observations above, what can you deduce about the factors affecting theinduced current caused by electromagnetic induction?Electrical GeneratorAn electrical generator is a device that converts mechanical energy to electrical energy,generally using electromagnetic induction. The source of mechanical energy may be areciprocating or turbine steam engine, water falling through a turbine or waterwheel,an internal combustion engine, a wind turbine, a hand crank, or any other source ofmechanical energy.In 1831-1832 Michael Faraday discovered that a potential difference is generatedbetween the ends of an electrical conductor that moves perpendicular to a magneticfield. He also built the first electromagnetic generator called the 'Faraday disc', a type ofhomopolar generator, using a copper disc rotating between the poles of a horseshoemagnet. It produced a small DC voltage, and large amounts of current.The Dynamo was the first electrical generator capable of delivering power for industry.A dynamo consists of a stationary structure which generates a strong magnetic field,and a set of rotating windings which turn within that field. On small machines themagnetic field may be provided by a permanent magnet; larger machines have themagnetic field created by electromagnets.The two types of generators are DC and AC generators: DC Generators - A cycledynamo and a car dynamo are examples of DC generators. They produce DC ACGenerators - AC Generators or alternators are used in power stations and industries toproduce AC.Principle; when a straight conductor is moved rapidly in a magnetic field, then acurrent is induced in the conductor. It is based on the phenomenon of electromagneticinduction.28

ConstructionMain Parts of the AC GeneratorAn AC generator consists of a magnet with concave cylindrical poles, an armature, anda current collecting arrangement. The current collecting arrangement consists of sliprings and brushes.‣ Armature is a soft iron core on which a coil having a large number of turns ofinsulated copper wire is wound. The concave Magnetic poles produce a radialmagnetic field.‣ The ends of the armature are connected to two slip rings. They rotate along withthe coil. The slip rings are made of metal and are insulated from each other.‣ There are two brushes B1 and B2 made of carbon. One end of each brush is incontact with the rotating slip rings and the other end is connected to an externalcircuit. Here the brushes are connected to a galvanometer but do not rotate withthe coil.‣ The axle is rotated mechanically from outside by some device –like a dieselengine, flowing water, steam or high-speed wind.29

Working‣ As the armature rotates about an axis perpendicular to the magnetic field, itkeeps on changing its relative orientation with respect to the field‣ Thus the flux keeps on changing continuously with time. This change inmagnetic flux induces an emf. If the outer terminals of the armature areconnected to an external circuit, an electric current flows through it, which isindicated by the deflection of the galvanometer needle‣ The direction of the induced emf is reversed after every half rotation of the coil.Thus in one rotation of the coil, the current changes its direction twice. Such acurrent, which changes its direction after equal intervals of time, is called analternating current (AC).The AC current produced in India has a frequency of 50 hertz (Hz). The coil is rotated atthe rate of 50 revolutions in 1 second. Because of these 50 revolutions, the currentchanges its direction 100 times in one second.To get a direct current (DC) generator, a split-ring type commutator must be used. Inthis arrangement, one brush is at all times in contact with the arm moving up in thefield while the other is in contact with the arm moving down.30

In case of split rings, the positionsof the segments of split rings havealso reversed when the currentinduced in the coil reverses i.ewhen the current directionreverses the brushes also come incontact with the reversedsegments. Hence, this current isunidirectional. It should be notedthat the position of the brushes is so arranged that the changeover of segments from onebrush to other takes place when the plane of the rotating coil is at right angles to theplane of the magnetic field lines or the lines of magnetic flux. It is so because in thatposition, the induced emf in the coil is zero.Another important point is that even now the current induced in the coil is alternatingas before. It is only due to the (rectifying) action of the split-rings (also calledcommutator) that it becomes unidirectional in the external circuit.ACTIVITY 5This simple experiment shows the reversibility of motor and dynamo effects.Apparatus and materialsFor each student groupSmall electric motorGalvanometer of 10 ohm resistance and range of 3.5 mA approxTwo Crocodile clipsTwo 4 mm Leads31

Copper wire 200 cm long , insulated with bare endsChoose electric motors which have an axle which can be readily turned by hand. Theymust also have two contacts where the crocodile clips can be attached.Procedure:a. Connect the electric motor to the galvanometer.b. Spin the motor and observe the galvanometer. You can spin the motor with afinger and thumb on the axle.c. Investigate the factors which affect the galvanometer reading. What happens if wereverse the direction of spin?d. If we are using a model electric motor, we can convert it so that it will generatealternating current (AC) as follows.1. Remove the rubber bands and undo the commutator wiring.2. Insulate both ends of the aluminium tube by wrapping adhesive tape aroundthem. Bring out the ends of the leads at opposite ends of the armature.3. Bare the leads for two or three centimetres, and wind the bare ends tightlyaround the aluminium tube. Make a brush at each end and connect up to themeter.32

Mutual Inductance - TransformerIf two coils of wire are brought into close proximity with each other so that the changeof magnetic flux in one links with the other, a voltage will be generated in the secondcoil. In such a scenario, that is when voltage impressed upon one coil induces a voltagein another, the associated phenomenon is called mutual inductance.The TRANSFORMER is a device specifically designed to produce, and use, the effectof mutual inductance between two or more coils.In practice, the transformer is the static device used to change high voltage low currentA.C into low voltage high current A.C and vice versa. We can also say that it transferselectrical energy from one electrical circuit to another.Working PrincipleIt is based on the principle of Mutual Inductance. When the primary coil is connected toan A.C source, the flux around this coil changes due to a continuous change in thevoltage across it. As the secondary coil is placed near the primary, nearly same amountof flux changes around secondary which gives rise to an induced EMF in it.A step down transformer isused, when it is required totransfer power at a lowervoltage and we have a higheramount of voltage available.In the reverse case, when it isrequired to transfer power ata higher voltage, a step uptransformer is used.33

Construction of transformerThe transformer consists of a soft iron core or the silicon steel core and two windingsattached to it i.e. primary winding (connected to AC source) and the secondarywinding (winding across which load is connected) such that core and the windings areinsulated from one another. Laminated iron core is used to minimize the effects of eddycurrents.What happens if DC current is provided to primary winding?If the transformer primary winding is provided with the direct current then the fluxproduced would not be varying in magnitude and remains constant. Hence, in such acase, there would not be any induced electro motive force in the secondary winding.Hence, a DC source, having a constant magnitude, cannot be used in a transformer tostep up or step down its DC voltage.A very useful property of transformers istheir ability to transform voltage and currentlevels according to a simple ratio,. This ratiois determined by the ratio of input andoutput coil turns. If the primary coil of atransformer is energized by an AC voltage,the amount of AC voltage induced in thesecondary coil will be equal to the inputvoltage multiplied by the ratio of output toinput wire turns in the coils. Conversely, thecurrent, through the windings of the outputcoil compared to the input coil, will followthe opposite ratio: if the voltage is increased34

from input coil to output coil, the current willbe decreased by the same proportion. Thisaction of the transformer is analogous to thatof mechanical gearsMathematicaly as per faraday‘s lawIf V1 and N1 represent voltage and number of turns in primary coil & V2 and N2 forsecondary coil thenV1 / V2 = N1 / N2Also sincepower output [P=VI]transformer is assumed to be 100% efficient, the power input is equal toHence V1 / V2 = N1 / N2 = I2 / I1A transformer designed to give a higher output voltage, compared to the voltageapplied across its input coil, is called a "step-up" transformer, while one designed to dothe opposite is called a "step-down" transformer. This is in reference to thetransformation of voltage that takes place. The current through each respective coil, ofcourse, follows the exact opposite proportion.35

REVIEW:• A transformer is a device made up of two or more coils in close proximity toeach other, with the express purpose of creating a condition of mutualinductance between the coils.• Transformers only work with changing voltages, not steady voltages. Thus,they may be classified as an AC device and not a DC device.Alternating CurrentAlternating current or AC means that the direction of current flowing in a circuit isperiodically changing and is constantly getting reversed back and forth. The electricalcurrent in our houses is an alternating current. This comes from power plants that areoperated by the electric company. Those big wires we see stretching across thecountryside are carrying AC current from the power plants to the loads, which are inour homes and businesses. The direction of current is switching back and forth a fixednumber of times—50 times in one second in countries like India and 60 times in eachsecond in U.S.A and other countries. We also express this by saying that theFREQUENCY of the alternating current is 50 hertz(50Hz) or 60 hertz (60Hz).Consider a case in which an electric light bulb is connected to an AC source ofelectricity through a switch. This is a series circuit using an AC source of electricity.Notice that the light bulb still lights but the electron current is constantly reversingdirections. The change in direction of the current flow happens so fast that the lightbulb does not have a chance to stop glowing or to show any changes in its glow. Thelight bulb glows uniformly both with a DC or an AC current. This is because the currentkeeps on heating up its filament irrespective of its direction of flow. The circuit isdelivering energy to the light bulb from the source, which, in this case, is a power plant.36

Direct Current vs. Alternating CurrentBatteries, fuel cells and solar cells all produce currents known as a direct current (DC).The positive and negative terminals of a battery are always, respectively, positive andnegative. Current always flows in the same direction between those two terminals.The power that comes from a power plant, on the other hand, is called alternatingcurrent (AC). The direction of the current reverses, or alternates, 60 times per second (inthe U.S.) or 50 times per second (in Europe, for example). The power that is available ata wall socket in the United States is 120-volt, 60-cycle per second AC power. In India, itis 220-volt,50 cycle per second AC power.Graphic representation of the intensity of the current as a function of time:Direct currentAlternating current37

The big advantage that alternating current provides for the power grid is the fact that itis relatively easy to change the voltage of the power, using a device called atransformer. Power companies save a great deal of money this way, using very highvoltages to transmit power over long distances.How does this work? Well, let's say that you have a power plant that can produce 1million watts of power. One way to transmit that power would be to send 1 millionamps at 1 volt. Another way to transmit it would be to send 1 amp at 1 million volts.Sending 1 amp requires only a thin wire, and not much of the power is lost as heatduring transmission. Sending 1 million amps would require a huge wire( very likely tobe unavailable) and would cause immense power losses during transmission.So power companies convert alternating current to very high voltages fortransmission (such as 1 million volts), then drop it back down to lower voltages fordistribution (such as 1,000 volts), and finally down to 120 volts (or 220 volts) inside thehouse for safety. A high degree of safety is provided now days by using GFCI outlets).An AC waveform can be sinusoidal, square, or sawtooth-shaped. Some AC waveformsare irregular or complicated. An example of sine-wave AC is common household utilitycurrent (in the ideal case). Square or sawtooth waves are produced by certain types ofelectronic oscillators, and by a low-end uninterruptible power supply (UPS) when it isoperating from its battery. Irregular AC waves are produced by audio amplifiers thatdeal with analog voice signals and/or music.The voltage of an AC power source changes from instant to instant in time. The effectivevoltage of an AC utility power source is usually considered to be the DC voltage thatwould produce the same power dissipation as heat in a load that can be assumed to bea pure resistance. The effective voltage for a sine wave is not the same as the peakvoltage. To obtain effective voltage from peak voltage, one has to multiply it by 0.707. Toobtain peak voltage from effective voltage, one needs to multiply by 1.414. For example,38

if an AC power source has an effective voltage of 117 V, typical of a household in theUnited States, the peak voltage is 165 V. For an Indian household, an effective voltage of220 volts, the peak voltage would be nearly311 volt.ACTIVITY 6Learning objective; Experiment shows the significant energy losses along any lowvoltagetransmission line.Material required:Two Power line terminal rodsTwo Retort standsTwo Lamps (12 V, 24 W) in lamp holdersTwo lengths of bare Eureka wires (28 SWG) 1.5 m eachDC Power supply of 0 to 12 VTwo DC voltmeters reading to at least 12 VDC Ammeter reading to at least 2 AProcedure:a. Fix two rods, which form the powerline terminals, horizontally in twobasses at a height of about 30 cm abovethe bench and roughly 1.5 m apart.b. Stretch two lengths of resistance wirebetween the terminals to form thepower line.c. Connect one of the two lamps directly39

to the 12 volt DC supply at the 'power station' end.d. Connect the supply directly to one of the terminal rods.e. Connect the second lamp to the other end of the power line, where it representsthe 'village'. Switch on the power supply. The 'village' lamp will just glow, incontrast with the fully-lit pilot lamp at the 'power station'.f. Observe the effect of connecting a second lamp in parallel with the single 'village'lamp.g. Connect a voltmeter in parallel with each of the lamps, and note the voltages.Electric Energy consumptionElectricity is one of the fundamental requirements of the humans in the present andfuture days. Electric energy rates are the rates on which the electricity is provided togeneral persons. The future of the modern industrial society is nothing but electricpower because practically every work requires electricity so that it gets done in theprescribed time. These large scale universal applications of electricity are one of thereasons for the relatively large electric energy rates.Electric energy rates are defined as the cost of one unit of electric energy used by anyuser. The electric energy rates are different in different countries.An electricity meter or energy meter is a device that measures the amount of electricenergy consumed by a residence, business, or an electrically powered device.Electricity meters are typically calibrated in billing units, the most common one beingthe kilowatt hour. Periodic readings of electric meters establish billing cycles andenergy used during a cycle.40

Unit of measurementKilowatt hour is equal to the amount of energy used by a load ofpower one kilowatt over a period of one hour. It, therefore, equals3,600,000 joules. Some electricity companies use the SI mega jouleinstead.Numerical Relation between SI and Commercial Unit ofElectrical EnergySI unit of energy is the joule.Commercial unit of energy is kWh.1 kWh = 1 kW x 1 h= 1000 W x 3600 s1 watt - second = 1 joule1 kWh = 3600000 JWORKSHEET 11. Calculate the power of aa. light bulb that uses 36J of electrical energy in 6 seconds.b. motor that uses 800J of electrical energy in 20 seconds.c. girl who performs 3000J of work in 6 seconds.d. car that uses 80000J of chemical energy in 2 seconds.41

2. Calculate the energy used by aa. light bulb of power 60W in 8 seconds.b. light bulb of power 40W in 2 minutes.c. Car of power 60kW in 10 seconds.d. light bulb of power 15W in 200 seconds.3. Calculate the work done by aa. Motor of power 2000W in 5 seconds.b. Generator of power 3MW in 7 days.4. How long does it take aa. light bulb of power 150W to produce 900J of energy.b. light bulb of power 60W to produce 7200J of energy5. Calculate the power of a door bell that uses 360kJ of electrical energy in 200 hoursQuestions on paying for electricity consumptionIn all of the questions below we assume that one electrical unit of energy (kilowatthour)costs Rs. 3/= each.1. How many kilowatt hours are used by a 3 kW device in 5 hours?2. What is the cost of using a 2 kW geyser for 4 hours?3. How long does it take a 2 kW geyser to use 1kWh?4. If you left on a computer of power 400 W on for the whole day, what would it cost?5. What is the cost of using a 700 W microwave for 10 minutes?42

WORKSHEET 21. In the diagram below, the conductor loop falls down into a magnetic field directedtoward the observer (out of the page). What is the direction of conventional currentinduced in the loop?2. The diagram below depicts a conducting loop falling straight down through auniform magnetic field directed toward the observer. What direction doesconventional current flow through loop?3. A transformer is used to change a 120 V, 3 A current to 2500 V.a. What kind of transformer is this?b. What is the ratio of secondary turns to primary turns?c. What current would be developed in the secondary coil?43

4. A step-up transformer has 100 turns on the primary coil and 500 turns on thesecondary coil. If this transformer is to produce an output of 4300 V with a 12 mAcurrent, what input current and voltage are needed?5. The current in an air-core solenoid is reduced from 3.99 A to zero over 5.9s. Thesolenoid has 2000 turns per meter and a cross-sectional area of 0.131 m 2 .Surrounding the solenoid near the center of its length is a second coil of 50 turns.a. What is the magnitude of the induced emf in the second coil?b. If the resistance of the second coil is 0.00409 ohm what is the induced current?6. When lightning strikes, nearby magnetic compass needles may be seen to jerk inresponse to the electrical discharge. No compass needle deflection results during theaccumulation of electrostatic charge preceding the lightning bolt, but only when thebolt actually strikes. What does this phenomenon indicate about voltage, current,and magnetism?7. Just as electricity may be harnessed to produce magnetism, magnetism may also beharnessed to produce electricity. The latter process is known as electromagneticinduction. Design a simple experiment to explore the phenomenon ofelectromagnetic induction.8. A small piece of metal wire is dragged across the gap between the pole pieces of amagnet in 0.5 sec.The magnetic flux between the pole pieces is known to be 8 x 10 -4Wb.Estimate the emf induced in the wire.9. Which magnet motion past the wire will produce the greatest voltmeter indication:perpendicular, parallel, or no motion at all?44

REVISION WORKSHEET1. The frequency of the a.c. Supply in a country equals 50 cycles per second. How manytimes does the current in this supply touch it's maximum value in one second?2. Is it possible for a current varying in a zigzag random way to be still classified as analternating current?3. We usually have to be careful and particular while connecting an ammeter or avoltmeter in a circuit but not so for the appliances we use at our homes. Why?4. Transformers are a necessary component during the supply and use of electricity.State one reason for this that you think is most important.5. Two coils are kept in close vicinity of each other. If the current, flowing in the firstcoil were switched off twice as fast as before, what is the likely effect on the secondcoil?6. A conductor is kept close to a magnet which is the moved away rapidly.The experiment is repeated but now the magnet is kept stationary and the coil ismoved away from it as fast as in the first case. Suggest the possible situations in45

which the observed effects in the two cases may be similar or different from eachother.7. A pair of coils, insulated from each other, are arranged so that a current flows in thefirst coil and the induced effects, if any, are observed in the second coil.Suppose the observation is taken in the U.S.A and in India.Are we likely to observe any difference in the two cases? Justify your conclusion.8. A conductor is situated in a rapidly changing magnetic field but the lines of themagnetic field always remain 'grazing' the conductor. Would there be any inducedcurrent in the conductor?9. Which form of energy gets converted into electric energy in a generator? Is theanswer dependent on the type of power station we are talking about?10. State two pints of difference between the current obtained from the mains and froma battery.46

RUBRICS OF ASSESSMENT FOR LEARNINGUnit 3 – Electromagnetic InductionParameter Learner is able toBeginning(1)Approaching(2)Meeting(3)Exceeding(4)Describe ElectromagneticinductionState and explainFleming‘s right hand ruleDescribe the factorsaffecting the currentinduced in a conductorplaced in a magneticfield.Describe the function andworking of a generatorDescribe the working of atransformer.Describe alternatingcurrentDescribe the transmissionof power in highvoltages.Understand the unitsused to measure electricpower.Resources:www.allaboutcircuits.com/vol_1/chpt_14/5.htmlen.wikipedia.org/wiki/Faraday's_law_of_induction47

CHEMISTRYUnit 3: Electricity and ChemistrySYLLABUS COVERAGESYLLABCore Oxidation reduction in terms ofelectron gain or loss of oxygen orhydrogen Working of electrolytic cells. Electrolysis of molten salts using inertelectrodes. Electrolysis of aqueous solutions ofelectrolytes using inert electrodes Electrolysis of aqueous solutions ofelectrolytes using reactive electrodesExtension Electrochemical theory ofrusting. Prevention of rusting usingelectrochemical theory Fuel cellUSUse of electrolysis in refining of metalslike copperUse of electrolysis in electroplatingExtraction of Al from bauxite Working of Electrochemical cellssimpleZn/Cu cells48

MATRIXCONTENT INTENDED LEARNING SKILL1. Warm up-Whole class approach,for brain storming, askinitiating questionssuggested in teachernotes2. Pre content oxidationreduction in terms ofgain or loss of oxygen orhydrogenContent-1oxidation reduction interms of electron gain orlossStudents research, discussin their groups and thenpresent their findingsbefore the class.Students complete the –I know and want to knowsections of the KWL sheetin groups of two and thenshare in the class.Activity-1Students perform theactivity to find the bestreducing and oxidisingagent of the given metals,this activity in another formthey have alreadyperformed in the previouschapter of ‘Metals’.In this unit they shouldwrite the ionic equationsfor the reaction taking placeand label oxidation halfand reduction halfreactions.CommunicatingInferringComparingCommunicatingInferringPredictingHypothesizing andControlling Variables,InvestigationClassifying49

Content-2Electrode ProcessesContent-3Applications ofelectrochemical series andthe working ofElectrochemical cellssimpleZn/Cu cellsActivity-2Worksheet-1Students understand that aredox reaction whencarried out indirectly maybe used to produceelectrical energy.Activity-3Worksheet-2The students- Describe the operationof the electrochemicalcell. write balancedoxidation and reductionhalf-reactions;Reasoning,Making connections,InvestigatingClassification, Relating todaily routine, learning bydoing.write balanced chemicalequations for theoverall reaction;construct a simplifieddiagram of the cell,including designationof anode and cathode,positive and negativeelectrode, direction ofelectron flow in theexternal circuit, anddirection of migration50

Content -4Electrolytic cellsContent-5electrolysis of molten saltsusing inert electrodesContent-6electrolysis of aqueoussolutions of electrolytesusing inert electrodesContent-7electrolysis of molten saltelectrolytes using reactiveelectrodesof ions within the cell.Worksheet-3Students record theirobservations of the activitiy4 and analyse howelectrolytic cells work interms of gain and loss ofelectrons.Students designate theelectrodes as cathode andanode.Activity-4Students should be able towrite the ionic equationsfor the reaction.Activity-5Students understand thatthe ions available in the cellare different than that wereavailable for molten saltsand hence there would be avariation in the productsformed.Students write the ions andmetal available foroxidation and reduction inthe cell and classify them asLearning by doing,ObservationExperiment/ LaboratoryManage, record andcommunicate informationResourcefulness, carefulobservation, application,Resourcefulness, carefulobservation, application,51

Content-8Applications of Electrolysisin metallurgy andelectroplatingPost ContentElectrochemical theory ofRusting of ironPost contentFuel cellsbeing available of oxidationor reduction and thenpredict the products ofelectrolysis.After this concept studentsare ready for the singleworksheet created for theactivities 4 to6Worksheet-3The students will be ableto- Describe applications ofelectricity in metallurgy Understand themetallurgy ofaluminium frombauxite ore. Understand the methodof refining copper usingelectrolysis.Worksheet-4Students relate rusting andits prevention to electricityand chemistry.As an extension studentsmay learn about the fuelcells.Appreciation ofcontribution in science,team workLearning by observationand reasoningLearning abouttechnologicaladvancements52

SCOPE DOCUMENTIntended Learning outcomes - CoreAt the end of this unit students would be able to –Describe oxidation and reduction in terms of gain or loss of oxygen / hydrogen.Describe oxidation and reduction in terms of gain or loss of electrons.Explain the working of electrolytic cellsObserve and explain electrolysis of molten salts using inert electrodes.Explain electrolysis of aqueous solutions of electrolytes using inert electrodesExplain electrolysis of aqueous solutions of electrolytes using reactive electrodesDescribe use of electrolysis in refining of metals like copperState the use of electrolysis in electroplatingExplain rusting of iron and methods to prevent rustingDescribe extraction of Al from bauxiteExplain the working of Electrochemical cells-simple Zn/Cu cellsLearning outcomes – ExtensionAt the end of this unit students would be able to –Explain electrochemical theory of rustingDescribe the working of a fuel cellSuggested ActivitiesExperiment-electrolysis, electroplatingExperiment-Making electrochemical cellsCross curricular linksHistory-.The process of development of the first electrochemical cell and theusage of electrochemistry in plating of one metal on the other.Economics- Loss of revenue due to rusting.53

Physics-.Production of electric current by virtue of chemical reactions andfinding the volts produced by a particular cell.Environmental Science- Saving pollution by using non-polluting energy source:the fuel cell.Biology- Transfer of nerve impulse caused by the electrical signals. The role ofelectrolytes in maintaining the balance in body.TEACHER’s NOTES FOR –TSSM(Teacher Student Support Material)This unit on ‘Electricity and Chemistry’ discusses the generation of electrical energy byvirtue of chemical reactions as well as carrying out of chemical processes by virtue ofelectrical energy. Students of grade X have some understanding of production ofelectricity and usage of dry cells to run battery operated devices. They also have a fairidea of inter-conversion of energy. The teacher should evolve the unit from these dayto-daylife experiences and ask them few probing questions to begin with. Afterstudying this unit, the learner will be able to:Learning objectives-CoreDescribe oxidation and reduction in terms of electron gain or loss of oxygen orhydrogen.Understand working of electrolytic cells.Carry out electrolysis of molten ZnBr2 salt using inert electrodes.Predict the product of electrolysis of molten salts using inert electrodes.Carry out electrolysis of aqueous solutions of electrolytes using inert electrodesPredict the product of electrolysis of electrolysis of aqueous solutions ofelectrolytes using reactive electrodes.Apply the knowledge of electrolysis in refining of metals like copper andextraction of Al from bauxite.54

Apply the knowledge of electrolysis in electroplating.Construct an electrochemical cell-simple Zn/Cu cell.Understand the production of electrical energy by harnessing the chemicalenergy of a reaction.Learning objectives-ExtensionApply the electrochemical theory to rusting of iron.Suggest methods for prevention of rusting using electrochemical theoryUnderstand the working of the cell of the future-Fuel cellThe students of grade 9 and 10 are in ‘The stage of formal experimentation’. Theteaching learning process for the students of this age should be structured and focusedaround-Their physical and biological environment.Emphasis on Scientific method Designing and conducting simple controlled experiments (Hypothesisformulation, data analysis and interpretation, Identifying the control, and thevariables)Concrete experience , analysis of the experience, leading to concept attainmentEmphasis on estimation, measurement, mapping and probabilityComprehension of Science LiteratureUse of formal laboratory apparatus to learn pre laboratory procedures such asweighing, measuring temperature, solution making, filtering, in addition to useof improvised Science learning kits.Constructing an overview of the unit is the first step in planning the unit. This couldbe done throughStep 1:- As a pre content exercise, prepare a web of related terms that come to yourmind - in the form of a concept web. Read about it.55

Step 2:- Next, organise the information into a logical pattern. You could keep a thumbrule, to move from simple to the complex idea.Step 3:- Having identified the key concepts and sub concepts get started to enrich eachof these and you could use illustrations and examples to represent the collectedinformation in the class interaction.Step 4:- Explore and identify the tasks to be undertaken, a few have been identified.These can always be improved. Mentally check each task for its practicalpossibility, and relevance to improve learners understanding about ‘Electricityand Chemistry’.Introduction- For a warm up to this unit-The teacher may start this unit by asking simple questions like-How do we get the electricity to run fans, air conditioners and other electricalequipments?What type of energy transformations take place during running of variouselectrical equipments?How is a dry cell able to provide electrical energy? What type of energytransformation takes place during lighting of a bulb using a dry cell? How the Apollo mission astronauts obtain the required energy and water inspace?The students may be allowed to do some library research in groups of two to fourfollowed by a group presentation to answer the above questions.After the presentation by the students the teacher may lead them to the desire to knowmore about the possibility of production of electricity by virtue of chemical reactions.Instead of following the same plan as given above the teacher may employ a variety ofmodes to communicate, such as discussion, individual/group work, oral/written orproject/ presentations. The under girdling concern to empower the learners with theskill for direct and extended observation, can bring amazing results. As teachers we will56

have to allow the students, the scope to make mistakes, for perfection, howsoever,asymptotic, is achievable through systematically sustained approach. This is the logicbehind the philosophy of Continuous and Comprehensive Evaluation.Many a times the tendency to over read the analysis, deflects our discussions toinconclusive statements. It would help us remember that data analysis is not anindependent activity. Rather, it must feedback to relate to discrete concepts. Theempirical (observation based) nature of science tends to communicate the preferencesfor practical activities, it is important to note that a 'practical' need not be reduced to anactivity only. Any activity conducted in the class, be it a discussion, demonstration oran experiment, would be insufficient till it gets transcribed into an experience. We canthen state that learning is an experiential activity.Teacher may tell the students that for understanding the production of electricitythrough chemical reactions or vice-versa we need to understand more about whathappens during the reaction.Pre-content activity-The teacher may ask the students about their knowledge of oxidation andreduction taking place during the reaction.The students may be asked to start the KWL sheets and write about what theyalready know about oxidation and reduction.The responses to above questions may be summed up or corrected by the teacherstarts by summarising the oxidation-reduction process in terms of loss and gain ofoxygen and hydrogen and then in terms of electrons. Activity-157

Content-1Oxidation Reduction in Terms of Electron Gain or LossTeacher brings the students to the concept attainment of how non spontaneous/nonfeasiblereactions studied in the previous sections may be made to occur using electricalenergy. The students perform an activity on finding the relative strength of metals.Activity-2 and Activity-3Content-2Redox Reactions and Electrode ProcessesIn the activity students have developed a reactivity series for the metals taken and theyunderstand that a reaction produced by dipping a more reactive metal in the solution ofa metal salt of less reactive metal is a redox reaction. Ask the students to write reactionbetween zinc metal and copper sulphate solution and then the following questions-1. Identify the metal which has gained electrons.2. Identify the metal which has lost electrons.3. What is electric current? How the current is carried from one place to another?(Lead the students to answer that electrons are the carriers of electric current.)4. If flow of electrons produces the electric current and all redox reactions involvetransfer of electrons then are we able to harness this energy to light a bulb or runa small fan?5. Should we see what modifications we can do in the activity performed so as toproduce electric current?Electrochemical CellsThe teacher may introduce the topic of electrolytic cells by talking to the students aboutsome real life experiences of generation of electricity, followed by the historicalbackground as given below.58

Leigh Galvani was the pioneer to generate an electrical current by bringing differentmetals strips (electrodes) in contact with a conducting solution would. In 1800,Alessandro Volta used this information to develop the first electrochemical cells usingmetal electrodes and aqueous salt solutions. He used copper and zinc metal with piecesof cardboard soaked in brine between the metal discs, in his first cell. He later createdhis first battery the voltaic pile by linking many of these cells together in series.Watch this video on animation of a galvanic cellhttp://www.youtube.com/watch?v=nNG5PMlHSoA&feature=relatedContent-3Applications of Electrochemical SeriesTake the students to concept attainment of development of electrochemical series/reactivity series and discuss the applications as-Predicting the maximum cell potential that may be generated by constructing acell.E 0 cell = E 0 reduction half - E 0 oxidation halfE 0 cell = E 0 cathode - E 0 anodePredicting the feasibility of a reaction.Ask students to discuss and reason out whether it would be possible to-‣ Store a solution of silver nitrate in a container made of zinc metal?‣ Store a solution of zinc nitrate in a container made of silver metal?Steps for making the predictions-Step-1Write the reaction as suggested in the questionEg 1: AgNO3 + Zn --- ZnNO3 + AgEg 2: ZnNO3 + Ag --- AgNO3 + Zn59

Step-2Write the E 0 cell expression-E 0 cell = E 0 reduction half - E 0 oxidation halfE 0 cell = E 0 Ag + - E 0 zn ++E 0 cell = 0.80 – (- 0.76)E 0 cell = + 1.56VStep-3As E 0 cell for the reaction is a positive value reaction is feasible so weshould not store silver nitrate in a container made of zinc metal.The students may compare the electrode potentials of the elements Agand Zn to make the predictions even without actual calculations. Theyshould understand that a metal higher up in the reactivity series having amore negative E 0 is more reactive and is able to displace a metal lower inthe reactivity series, i.e. element having a less negative or positive E 0value.On the same lines the second reaction is not feasible as E 0 for this reactionwould be negative which suggests that the reaction is not feasible andhence we can easily store nitrate in a container made of silver metal.The teacher facilitates the students in construction of an electrochemical cellwith special reference to construction of a salt bridge and production ofelectrical energy. The reading on the volt meter will surely bring an AHA!Moment for the students. Activity-2Predicting the products of electrolysisAsk the students to write all the possible ions in the given salt solution, theyshould be able to tell that positively charged ions will move towards the cathode60

to get reduced by taking up electrons and get reduced. On the other hand anionswill move towards the anode to lose electrons and get oxidised.At anode: The element having lower E 0 value gets oxidised.At cathode: The element having higher E 0 value gets reduced.Content-4Electrolytic CellsTeacher may first show the demonstration of electrolysis of CuSO4 and then teach thetheory for electrolysis of molten salts using inert electrodes.Teacher facilitates the students to construct an electrolytic cell for electrolysis of waterand then takes up the theory of electrolysis of aqueous salts with special reference toelectrolysis of brine (aqueous NaCl).Activity-4Content-5Electrolysis of Molten Salts Using Inert ElectrodesThe teacher leads the students to predict the products of electrolysis of an molten saltusing inert electrodes.Activity-5Anecdotes: If the bulb does not light when testing the circuit, check that the electrodes arenot cracked and circuit is complete in all respects. Be careful while melting zinc chloride as its boiling point which is about 730°Ccan easily be reached by the combination of the heat from the Bunsen burner andthe electric current. If the zinc chloride does begin to boil, it can boil over fromthe crucible and will also produce fumes of zinc chloride in the air. These rapidlyturn back to the solid, forming a fine powder. Students might get confusedseeing the fumes and gather that chlorine gas is being formed. Therefore do notheat the molten zinc chloride too strongly.61

Do not remove the Bunsen burner and cool the salt while still electrolysing it, inorder to show that the salt only conducts when molten. The heating effect of theelectric current will keep the salt molten for several minutes, and when it doescool, a crust forms which is very difficult to re-melt.Content-6Electrolysis of Aqueous Solutions of Electrolytes Using Inert ElectrodesThe teacher facilitates the students in construction of an electrolytic cell with specialreference to carrying out non-spontaneous reactions using electrical energy. Teachershould take up electrolysis of water and electrolysis of brine. Students prepare simpleelectrolytic cell for electrolysis of water and understand the splitting of water intohydrogen gas and oxygen gas. The volume of the two gases collected should beanalysed. It should be understood that H2 is collected at the cathode and O2 is collectedat the anode in the ratio 2:1Activity-6Content-7Electrolysis of Molten Salts Using Reactive ElectrodesThe teacher leads the students to predict the products of electrolysis of an aqueous saltusing active electrodes.Content-8Applications of Electrolysis in Metallurgy and ElectroplatingThe teacher may introduce the students to applications of electrolysis in electroplating,refining of metals like copper and extraction of metals from their ore specifically Alfrom bauxite.Post content-1 (extension)Electrochemical Theory of Rusting of IronVideo for electrochemical theory of rustinghttp://www.youtube.com/watch?v=OdMBczqhPWo62

TEACHERSTUDENTSUPPORTMATERIAL(TSSM)63

An OverviewThis unit provides an overview of the generation of electrical energy by virtue ofchemical reactions as well as carrying out of chemical processes by virtue of electricalenergy. The knowledge of production of electricity and usage of dry cells to run batteryoperated devices and idea of inter-conversion of energy is a prerequisite for theunderstanding of this unit.Pre content: Creating the context –completion of the ‘Know’ and ‘Want to know’sections of the KWL sheets.I Know(about this topic)Activity-1I Want to Know(about this topic)I have learntContent-1Oxidation Reduction in Terms of Electron Gain or LossLearning objectives:The students will be able to- Define oxidation and reduction in terms of gain or loss of oxygen and hydrogen.Define oxidation and reduction in terms of transfer of electrons.Write half reactions and net ionic equations involving oxidation-reductionprocesses.Oxidation-Reduction Reactions Oxidation and reduction in terms of hydrogen transferThese are old definitions which aren't used very much nowadays. The most likelyplace you will come across them is in organic chemistry. Oxidation is loss of hydrogen.64

Reduction is gain of hydrogen. Oxidation and reduction in terms of oxygen transferOxidation is gain of oxygen.Reduction is loss of oxygen.The term oxidation was originally used to describe reactions in which an elementcombines with oxygen.Example: The reaction between magnesium metal and oxygen to form magnesiumoxide involves the oxidation of magnesium.2Zn(s) + O2 -----2ZnO(s)The term reduction comes from the Latin stem meaning "to lead back." Anythingthat that leads back to magnesium metal therefore involves reduction.The reaction between zinc oxide and carbon at high temperature to form zinc metaland carbon monoxide is an example of the reduction of zinc oxide to zinc metal. Oxidation and reduction in terms of electron transferOxidation-reduction reactions may also be expressed as those involving the transferof electrons from one atom to another. From this perspective, the reaction betweenzinc and oxygen is written as follows.2 Zn+ O2 2 [Zn 2+ ][O 2- ]In the course of this reaction, each zinc atom loses two electrons to form an Zn 2+ ion.Zn Zn 2+ + 2 e -And, each O2 molecule gains four electrons to form a pair of O 2- ions.O2 + 4 e - 2 O 2-65

Thus in terms of loss and gain of electrons oxidation and reduction may be conceivedas-Loss of electrons=OxidationGain of Electrons=ReductionFollowing mnemonic may be used to remember this-Since electrons can neither be created nor destroyed reduction and oxidation always gohand in hand, thus –Reduction + Oxidation = REDOX Oxidation Number. It is the charge assigned to an atom of a compound or an ionaccording to some arbitrary rules. It is equal to the number of electrons in thevalence shell of an atom, that are gained or lost completely or to a large extent bythat atom while forming a bond in a compound.For Example:Iron forms a number of different ions - for example, Fe 2+ and Fe 3+ . If you think abouthow these might be produced from Fe metal, the 2+ ion will be formed by oxidising themetal by removing two electrons:Fe--------- Fe 2+ + 2 e -The Iron metal is in an oxidation state of +2 in the above example.Removal of another electron gives the Fe 3+ ion:Fe 2+ --------- Fe 3+ +e -Iron metal has gained an oxidation state of +3 in the above example.What if you add electrons to the element? Electrons can’t be added to metals but thismay be done for non metals like oxygen.O+ 2e - --------- O 2-Thus here oxygen has an oxidation state of -2.66

SummaryOxidation state shows the total number of electrons which have been removed from anelement (a positive oxidation state) or added to an element (a negative oxidation state)to get to its present state.Oxidation involves an increase in oxidation stateReduction involves a decrease in oxidation stateRecognising this simple pattern is the single most important thing about the concept ofoxidation states. If you know how the oxidation state of an element changes during areaction, you can instantly tell whether it is being oxidised or reduced without havingto work in terms of electron-half-equations and electron transfers.Working out oxidation states-RULESThe oxidation state of an uncombined element is zero. That's obviously so,because it hasn't been either oxidised or reduced yet! This applies whatever thestructure of the element - whether it is, for example, Xe or Cl2 or S8, or whether ithas a giant structure like carbon or silicon.The sum of the oxidation states of all the atoms or ions in a neutral compound iszero.The sum of the oxidation states of all the atoms in an ion is equal to the charge onthe ion.The more electronegative element in a substance is given a negative oxidationstate. The less electronegative one is given a positive oxidation state. Rememberthat fluorine is the most electronegative element with oxygen second.Some elements almost always have the same oxidation states in theircompounds:67

Elementusual oxidation stateExceptionsGroup 1 metals always +1Group 2 metals always +2Oxygen usually -2Hydrogen usually +1except in peroxides andF2Oexcept in metal hydrideswhere it is -1Fluorine always -1Chlorine usually -1except in compoundswith O or FThe reasons for the exceptionsHydrogen in the metal hydridesMetal hydrides include compounds like sodium hydride, NaH. In this, the hydrogen ispresent as a hydride ion, H - . The oxidation state of a simple ion like hydride is equal tothe charge on the ion - in this case, -1.Alternatively, you can think of it that the sum of the oxidation states in a neutralcompound is zero. Since Group 1 metals always have an oxidation state of +1 in theircompounds, it follows that the hydrogen must have an oxidation state of -1 (+1 -1 = 0).Oxygen in peroxidesPeroxides include hydrogen peroxide, H2O2. This is an electrically neutral compoundand so the sum of the oxidation states of the hydrogen and oxygen must be zero.Since each hydrogen has an oxidation state of +1, each oxygen must have an oxidationstate of -1 to balance it.68

Oxygen in F2OThe problem here is that oxygen isn't the most electronegative element. The fluorine ismore electronegative and has an oxidation state of -1. In this case, the oxygen has anoxidation state of +2.Chlorine in compounds with fluorine or oxygenThere are so many different oxidation states that chlorine can have in these, that it issafer to simply remember that the chlorine doesn't have an oxidation state of -1 in them,and work out its actual oxidation state when you need it. You will find an example ofthis below.Examples of working out oxidation statesWhat is the oxidation state of chromium in Cr 2+ ?That's easy! For a simple ion like this, the oxidation state is the charge on the ion - inother words: +2 (Don't forget the + sign.)What is the oxidation state of chromium in CrCl3?This is a neutral compound so the sum of the oxidation states is zero. Chlorine has anoxidation state of -1. If the oxidation state of chromium is n:n + 3(-1) = 0n = +3 (Again, don't forget the + sign!)What is the oxidation state of chromium in Cr(H2O)6 3+ ?This is an ion and so the sum of the oxidation states is equal to the charge on the ion.There is a short-cut for working out oxidation states in complex ions like this where themetal atom is surrounded by electrically neutral molecules like water or ammonia.The sum of the oxidation states in the attached neutral molecule must be zero. Thatmeans that you can ignore them when you do the sum. This would be essentially thesame as an unattached chromium ion, Cr 3+ . The oxidation state is +3.What is the oxidation state of chromium in the dichromate ion, Cr2O7 2- ?69

The oxidation state of the oxygen is -2, and the sum of the oxidation states is equal tothe charge on the ion. Don't forget that there are 2 chromium atoms present.2n + 7(-2) = -2, thus n = +6Oxidizing Agents and Reducing AgentsLet's consider the role that each element plays in the reaction in which a particularelement gains or loses electrons.When magnesium reacts with oxygen, the magnesium atoms donate electrons to O2molecules and thereby reduce the oxygen. Magnesium therefore acts as a reducingagent in this reaction.2 Mg + O2 2 MgOreducingagentThe O2 molecules, on the other hand, gain electrons from magnesium atoms andthereby oxidize the magnesium. Oxygen is therefore an oxidizing agent.2 Mg + O2 2 MgOoxidizingagentOxidizing and reducing agents therefore can be defined as follows. Oxidizing agents gainelectrons. Reducing agents lose electrons.The table below identifies the reducing agent and the oxidizing agent for some of thereactions One trend is immediately obvious: The main group metals act as reducingagents in all of their chemical reactions. The Relative Strength of Metals as Reducing AgentsWe can determine the relative strengths of a pair of metals as reducing agents bydetermining whether a reaction occurs when one of these metals is mixed with a saltof the other. Consider the relative strength of iron and aluminum, for example.70

Nothing happens when we mix powdered aluminum metal with iron(III) oxide. Ifwe place this mixture in a crucible, however, and get the reaction started byapplying a little heat, a vigorous reaction takes place to give aluminum oxide andmolten iron metal.2 Al(s) + Fe2O3(s) Al2O3(s) + 2 Fe(l)By assigning oxidation numbers, we can pick out the oxidation and reduction halvesof the reaction.Aluminum is oxidized to Al2O3 in this reaction, which means that Fe2O3 must be theoxidizing agent. Conversely, Fe2O3 is reduced to iron metal, which means thataluminum must be the reducing agent. Because a reducing agent is alwaystransformed into its conjugate oxidizing agent in an oxidation-reduction reaction,the products of this reaction include a new oxidizing agent (Al2O3) and a newreducing agent (Fe).Reference Links:http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch9/redox.phphttp://www.chemguide.co.uk/inorganic/redox/oxidnstates.html71

Activity-2Aim: To check spontaneity of reaction between a metal and salt solution of anothermetal.Materials Required:4 cleaned strips of each of the following metals , Zinc, Lead, Magnesium andSilver or iron may be substituted)0.1 M nitrate solutions of each of the elements above.oooooSilver nitrateIron ( III) nitrate if silver is substituted by ironCopper (II) nitrateLead (II) nitrateZinc nitrateProcedure:Perform the tests indicated below by adding cleaned strips of the metal elementto the solutions in separate test tubes.indicate with a check mark if there is evidence of a reaction.Metal / Solutions Cu (NO3)2 AgNO3 Pb(NO3)2 Zn(NO3)2Cu (s)Ag or Fe (s)Pb (s)Zn (s)Concluding Task:Write the nonionic and net ionic reaction for each of the single displacementreactions that occur.72

Indicate if the reaction was spontaneous or not.Label the oxidized and reduced species in each test.Write the half reaction for the reduction of each metal.Label the oxidizing agent (aqueous ion) and reducing agent. (metal strip).Which metal strip was the best reducing agent.Create a list of the half reactions of the reducing agent from best to least.Reference Links:http://www.saskschools.ca/curr_content/chem30/modules/module8/lesson1/lspont.htmlWORKSHEET-1Q1. Determine which element is oxidized and which is reduced when magnisiumreacts with nitrogen to form magnesium nitride.6 Mg(s) + 2N2(g) 2 Mg3N2(s)Q2. Determine which atom is oxidized and which is reduced in the following reaction2 Na(s) + 2 H2O(l) 2Na + (aq) + 2OH - (aq) + H2(g)Q3. Identify the oxidizing agent and the reducing agent in the following reaction.2Li(s) + H2(g)2 LiH(s)Q4. Use the following equations to determine the relative strengths of sodium,magnesium, aluminum, and calcium metal as reducing agents.2 Na + MgCl2 -- 2 NaCl + MgAl + MgCl2--- no reactionCa + MgCI2 ---- CaCI2 + MgCa + 2 NaCl-- no reaction73

Q5. In each of the following equations, indicate the element that has been oxidizedand the one that has been reduced. You should also label the oxidation state ofeach before and after the process:1) 2 Na + FeCl2 2 NaCl + Fe2) 2 C2H2 + 5 O2 4 CO2 + 2 H2O3) 2 PbS + 3 O2 2 SO2 + 2 PbO4) 2 H2 + O2 2 H2O5) Cu + HNO3 CuNO3 + H26) AgNO3 + Cu CuNO3 + AgReference Links:http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch9/redox.phphttp://misterguch.brinkster.net/pra_equationworksheets.htmlContent 2Redox Reactions and Electrode ProcessThe feasible reactions in activity-1 are redox reactions. During these reactions a transferof electrons takes place. But we are not able to harness the energy produced as electricalenergy because the transfer of electrons take place directly through the solution. Weshould modify the experiment in such a manner that for the same redox reactiontransfer of electrons takes place indirectly through a circuit. Let us take example of thezinc-copper sulphate reaction, for making the reaction occur indirectly it necessitatesthe separation of zinc metal from copper sulphate solution. So we take copper sulphatesolution in a beaker and put a copper strip or rod in it. We also take zinc sulphateelectrode is known as electrode potential. If the concentration of each species takingpart in the electrode reaction is unity and further the reaction is carried out at 298K,then the potential of each electrode is said to be the Standard Electrode Potential.74

By convention, the standard electrode potential (E 0 ) of hydrogen electrode is 0.00 volts.The electrode potential value for each electrode process is a measure of the relativetendency of the active species in the process to remain in the oxidised/reduced form. Anegative E 0 means that the element is a stronger reducing agent than hydrogen. Apositive E 0 means that the element is a weaker reducing agent than the hydrogen. Thestandard electrode potentials are very important and we can get a lot of other usefulinformation from them. The values of standard electrode potentials for some selectedelectrode processes (reduction reactions) are given in Table below. You will learn moreabout electrode reactions and cells in higher grades.The Working of Electrochemical Cells-Simple Zn/Cu CellsLearning objectives:The students will be able to- Describe the operation of an electrochemical cell;write balanced oxidation and reduction half-reactions;write balanced chemical equations for the overall reaction;75

Sketch a simplified diagram of the cell, including designation of anode andcathode, positive and negative electrode, direction of electron flow in the externalcircuit, and direction of migration of ions within the cell.ELECTROCHEMICAL CELLS (BATTERIES)Parts of a Voltaic CellThe electrochemical cell is actually composed of two half cells. Each half cell consists ofone conducting electrode ( a solid ) and a conducting solution called electrolyte. In mostcells the conducting solution is a moist paste, containing only enough solution for thecell to operate efficientlyOxidation occurs in one half cell and this produces electrons and reduction occurs in theother half cell and this accepts electrons. The flow of electrons does not start until thebattery or cells are have their electrodes connected by an external conducting wire likecopper.How Electrochemical cells work?When the two half cells, consisting of a metal electrode and a conducting solution areconnected with an external wire, the strongest oxidizing agent will undergo a reductionin one half cell and the strongest reducing agent will undergo an oxidation in the otherhalf cell. Tables of the strength of oxidizing and reducing agent can be found in anygood chemistry textbook.Key Points about the electrochemical cell1) Cathode: The electrode (solid) at which reduction occurs is termed as the cathodeand is positively charged.2) Anode: The electrode (solid) at which the oxidation occurs is called the anode and isnegatively charged as electrons are produced at this electrode.76

3) Direction of current flow: The electrons produced at the anode travel along theexternal wire from anode to the cathode were they are used to reduce the strongestoxidizing agent. This happens because the strongest oxidizing agent has a greaterattraction for electrons and literally pulls them off the strongest reducing agent.4) Spontaneity: The reaction in an electrochemical cell is always spontaneous.5) Ion flow: In the operating electrochemical cell, positive ions (cations) in theconducting solutions migrate toward the collection of electrons on the positiveelectrode or cathode, while negative ions migrates (move) toward the negativeelectrode termed the anode .Representing cellsAn electrochemical half cells is represented, using the following notation:A vertical line is used to indicate the separation of the solution and the electrode(solid).A copper half cell is represented below.Cu2+ | Cu (s)SolutionElectrodeThe entire electrochemical cell is represented by placing the two half - cells side by sideand separating them with two vertical lines.The oxidation half - cell is written first and the solution and electrode positions arereversed. The reduction half - cell is written second.A zinc - copper cell is represented below.Zn (s) | Zn 2+ (aq) || Cu 2+ (aq) | Cu (s)electrode solution solution electrodeOxidation half cellSaltbridgeReduction half cell77

EXAMPLE OF AN ELECTROCHEMICAL CELLA zinc/copper electrochemical cell (voltaic cell) is shown belowThe Cu-Zn cell:We take copper sulphate solution in a beaker and put a copper strip or rod in it. We alsotake zinc sulphate solution in another beaker and put a zinc rod or strip in it. Nowreaction takes place in either of the beakers and at the interface of the metal and its saltsolution in each beaker both the reduced and oxidized forms of the same species arepresent. These represent the species in the reduction and oxidation half reactions. Aredox couple is defined as having together the oxidised and reduced forms of asubstance taking part in an oxidation or reduction half reaction. Now we put the beakercontaining copper sulphate solution and the beaker containing zinc sulphate solutionside by side. We connect solutions in two beakers by a salt bridge (a U-tube) containinga solution of potassium chloride or ammonium nitrate usually solidified by boiling withagar agar and later cooling to a jelly like substance. This provides an electric contactbetween the two solutions without allowing them to mix with each other. The zinc andcopper rods are connected by a metallic wire with a provision for an ammeter and aswitch. When the switch is in the off position, no reaction takes place in either of thebeakers and no current flows through the metallic wire. As soon as the switch is in theon position, we make the following observations:1. The transfer of electrons now does not take place directly from Zn to Cu 2+ butthrough the metallic wire connecting the two rods as is apparent from the arrowwhich indicates the flow of current.2. The electricity from solution in one beaker to solution in the other beaker flowsby the migration of ions through the salt bridge. We know that the flow ofcurrent is possible only if there is a potential difference between the copper andzinc rods known as electrodes here.78

The apparatus acts as a battery. Current will flow in the wire, as shown by an ammeterA in the circuit. The copper electrode is found to be the positive electrode of the cell,with the zinc being the negative electrode. The potential difference of the cell depends,amongst other things, on the concentration of the solutions in the electrodecompartments and the temperature. When, in this cell, they are both 1.0 M the potentialdifference is about 1.1 volt.The following redox reaction occurs:The reaction is a combination of two half reactions whose addition gives the overall cellreaction:The compartment on the right is the site for the oxidation half-reaction:The zinc electrode, (where oxidation takes place) is called the ANODE, while thecopper electrode (where reduction takes place ) is called the CATHODE.79

When both the electrolyte concentrations are 1.0 mol.dm -3 and the temperature is 25 ºC,the cell is said to be a STANDARD CELL.Activity-3Students can refer the given site for construction and operation of a simple galvaniccellhttp://www.woodrow.org/teachers/ci/1986/exp28.htmlWORKSHEET-2The diagram shows a standard Cu/Zn electrochemical cell.80

Q1. The electrolyte in the cathode compartment isa. 1.0 M CuSO4b. 0.1 M ZnSO4c. 0.1 M CuSO4d. 1.0 M ZnSO4Q2. There is a clockwise electron flow in the wire. Which one of the followingstatements is true?a. Zinc is the cathodeb. Copper is the right-hand electrodec. Anions move from left to right in the salt bridged. Copper ions are formed at the anodeQ3. If the electron flow in the wire is anticlockwise, the reaction taking place in theright-hand half-cell is1. Zn 2+( aq) + 2e- → Zn(s)2. Cu 2+( aq) + 2e- → Cu(s) -3. Cu(s) → Cu 2+( aq) + 2e4. Zn(s) → Zn 2+( aq) + 2e -Content-3APPLICATIONS OF ELECTROCHEMICAL SERIESThe electrochemical series/ reactivity series have various applications in daily life andvarious industrial processes-Predicting the maximum cell potential that may be generated by constructing acell.E 0 cell = E 0 reduction half - E 0 oxidation halfE 0 cell = E 0 cathode - E 0 anode81

Predicting the feasibility of a reaction.Steps for making the predictions-Step-1Write the reaction as suggested in the questionEg 1: AgNO3 + Zn --- ZnNO3 + AgEg 2: ZnNO3 + Ag --- AgNO3 + ZnStep-2Write the E 0 cell expression-E 0 cell = E 0 reduction half - E 0 oxidation halfE 0 cell = E 0 Ag + - E 0 zn ++E 0 cell = 0.80 – (- 0.76)E 0 cell = + 1.56VStep-3As E 0 cell for the reaction is a positive value reaction is feasible so weshould not store silver nitrate in a container made of zinc metal.You may even compare the electrode potentials of the elements Ag and Znto make the predictions without actual calculations. A simple fact toremember is that a metal higher up in the reactivity series having a morenegative E 0 is more reactive and is able to displace a metal lower in thereactivity series, i.e. element having a less negative or positive E 0 value.On the same lines the second reaction is not feasible as E 0 for this reactionwould be negative which suggests that the reaction is not feasible andhence we can easily store nitrate in a container made of silver metalPredicting the products of electrolysisAsk the students to write all the possible ions in the given salt solution, theyshould be able to tell that positively charged ions will move towards the cathode82

to get reduced by taking up electrons and get reduced. On the other hand anionswill move towards the anode to lose electrons and get oxidised.At anode: The element having lower E 0 value gets oxidised.At cathode: The element having higher E 0 value gets reduced.Content-4Electrolytic CellsLearning objectives:The students will be able to-• Describe how an electrolytic cell works.• Set up an electrolytic cell and identify the oxidizing and reducing agents.ELECTROLYTIC CELLSIt is possible to use electrical energy to cause non-spontaneous redox reactions to occur.For example, electricity can be used to decompose molten sodium chloride into itscomponent elements:2 NaCl (l)---- 2 Na (l)+ Cl2 (g)Such processes, which are driven by an outside source of electrical energy, are calledelectrolysis reactions and take place in electrolytic cells.An electrolytic cell consists of two electrodes in a molten salt or a solution. The cell isdriven by a battery or some other source of direct electrical current. The battery acts asan electron pump, pushing electrons into one electrode and pulling them from theother. The electrode at which the reduction occurs is called the cathode, and theelectrode at which oxidation occurs is called the anode. In the electrolysis of moltenNaCl, shown in Figure Na + ions pick up electrons and are reduced to Na at the cathode.83

Electrolysis of molten sodium chloride. Cl – ions are oxidized to Cl2(g) at the anode, and Na + ionsare reduced to Na(l) at the cathode.As the Na + ions near the cathode are depleted, additional Na + ions migrate in. Similarly,there is net movement of Cl – ions to the anode, where they are oxidized. The electrodereactions for the electrolysis of molten NaCl are summarized as follows:Cathode: 2 Na + (l) + 2e - -- 2 Na (l)Anode: 2Cl - (l) ---- Cl2 (g) + 2e -Overall Reaction: : 2 Na + (l) + 2Cl - (l)------ 2 Na (l) + Cl2 (g)ACTIVITY-4Aim: To study the parts of an electrolytic cell and carry out an electrolytic reaction, i.e anon spontaneous reaction using electrical energy.Materials required:9 volt batterytwo carbon rods (can be taken from pencils ; pencil leads; which are made ofgraphite)copper(II) sulphate solution84

2 wires with alligator clips on the end.250 ml beaker or other container to hold solution.Procedures:1/2 fill a 250 ml beaker with copper (II) sulphate.Attach the wires to the positive and negative terminals of the battery.Attach the alligator clip ends to graphite rods (pencil leads) and place thegraphite rods in the solution.Observe the graphite rods for 5 minutes. What is happening?Analysis:Describe the reaction that is occurring at the positive electrode (graphite rodattached to the +ve terminal). This is the anode and is an oxidation reaction.Write the reaction that would be happening.Repeat the question above but for the negative electrode (graphite rod attachedto the - terminal). This is the cathode.Resource:http://www.saskschools.ca/curr_content/chem30/modules/module8/lesson3/labelectrolysis.htmContent 5Electrolysis of Molten Salts Using Inert Electrodes85

Activity-5Learning objectives:The students will be able to-Understand the general concepts of electrolysis.Understand the meaning of the term electrolysis.Predict the products of electrolysis of a molten salt using inert electrodes.This demonstration shows that an ionic salt will conduct electricity when molten butnot when solid. Zinc chloride is used - this will melt at Bunsen burner temperatures.Bring students up in groups of 2 or 3 to view the experiment. They should note at whichelectrode bubbles are forming but must avoid smelling the bleachy smell ( be aware thatmany students are asthmatic). They should be able to see crystals of zinc around thenegative electrode.Aim: To carry out electrolysis of molten zinc chloride and study the products ofelectrolysis.Materials required:Graphite electrodes, 2, supported in an electrode holder or bungAmmeter and/or bulb (in holder), Eye protection, Low voltage (0-12 V) Bunsen burner,tripod stand and heat resistant matPipe-clay triangle, Crucible, Clamp and stand, Metal spatula, Tongs, Plastic beaker,Filter paper and funnel, Indicator paper and/or starch-iodide paper, Solid zinc chloride86

Procedure:Set the tripod, Bunsen burner and pipe-clay triangle on the heat-resistant mat.Adjust and let the crucible sit onto the pipe-clay triangle, ensuring that there is inno danger of falling through.Set up the electric circuit with the ammeter, bulb and electrodes in series. Checkthat the circuit is complete by touching the circuit at the electrodes with a key orthe metal spatula.Clamp the electrodes taking care that they almost touch the bottom of thecrucible but do not touch each other.Fill the crucible upto 5 mm of the top with the powdered zinc chloride. As itmelts the solid will shrink in volume as air escapes and it is important that thelevel of the molten salt does not drop below the level of the bottom of theelectrodes. Ensure that the leads are well out of the way of the Bunsen flame.Using long electrodes can help with this.87

Repeating the process with solid zinc chloride• Begin to heat the crucible with a low to medium Bunsen flame. Watch the leads,and the bung if you are using one, to ensure that you are not over-heating them.• The zinc chloride takes about 3 or 4 minutes to melt. It may be tempting to use aroaring Bunsen flame to speed up the melting, but if you do so the zinc chloridecan form a crust over the top. This will prevent students from seeing what isgoing on, and the liquid salt may boil.• As the salt melts, the bulb will light up and/or the ammeter will give a reading.Turn the Bunsen down a bit at this point. There will be some heating effect fromthe electric current which may be enough on its own to keep the zinc chloridemolten (Same is followed in the industrial electrolysis of aluminium oxide.)• Bubbles of gas will be seen at the positive electrode. The gas can be confirmed aschlorine by holding moist indicator paper close to the bubbles - it will go red andthe edges may start to bleach. A more convincing test is to use moist starchiodide paper which will go black. It is also possible to see crystals of zinc formingon the negative electrode. These can form a bridge across the electrodes,effectively shorting them.• Electrolyse the molten salt for about 15 minutes, with the current adjusted toabout 0.5 A. Check every few minutes that the current remains roughly constantas there is a tendency for it to slowly increase.• After 15 minutes, turn off the power pack and Bunsen burner and remove theelectrodes from the crucible. If this is not done while the salt is still molten theelectrodes will stick.• Leave the crucible to cool for about 10 minutes. You may be able to see zinccrystals on both the electrode and on the surface of the mixture in the crucible.You could stop at this point, but to convince students that a metal really has beenmade you can separate the zinc from the remaining zinc chloride.88

Separating the zincaWhen the crucible is cool to the touch, put it into a beaker of distilled water. (If thewater is at all basic like most hard tap waters, the zinc ions will flocculate forminglarge particles which are far harder to remove from the zinc metal.) The zincchloride will dissolve (which may take some time) and can be decanted off. Swirlthe beaker which will cause the zinc metal to concentrate in the centre of thebeaker and decant off most of the liquid.b. Filter the remainder and show students the shiny pieces of metal left on the filterpaper. Dry the pieces of metal carefully between further sheets of filter paper andthen test with a circuit tester to prove that you have a metallic product.Given that the starting material was zinc chloride and you have made chlorine, moststudents will have little difficulty in accepting that the metal is zinc.(ii) THE ELECTROLYSIS OF MOLTEN NaClAn idealized cell for the electrolysis of sodium chloride is shown in the figurebelow. A source of direct current is connected to a pair of inert electrodesimmersed in molten sodium chloride. Because the salt has been heated until itmelts, the Na + ions flow toward the negative electrode and the Cl - ions flowtoward the positive electrode.When Na + ions collide with the negative electrode, the battery carries a largeenough potential to force these ions to pick up electrons to form sodium metal.Negative electrode (cathode): Na + + e - Na89

Cl - ions that collide with the positive electrode are oxidized to Cl2 gas, whichbubbles off at this electrode.Positive electrode (anode): 2 Cl - Cl2 + 2 e -The net effect of passing an electric current through the molten salt in this cell is todecompose sodium chloride into its elements, sodium metal and chlorine gas.Electrolysis of NaCl:Cathode (-): Na + + e - NaAnode (+): 2 Cl - Cl2 + 2 e -The potential required to oxidize Cl - ions to Cl2 is -1.36 volts and the potentialneeded to reduce Na + ions to sodium metal is -2.71 volts. The battery used to drivethis reaction must therefore have a potential of at least 4.07 volts.This example explains why the process is called electrolysis. The suffix -lysis comesfrom the Greek stem meaning to loosen or split up. Electrolysis literally uses anelectric current to split a compound into its elements.electrolysis2 NaCl(l) 2 Na(l) + Cl2(g)This example also illustrates the difference between voltaic cells and electrolyticcells. Voltaic cells use the energy given off in a spontaneous reaction to do electricalwork. Electrolytic cells use electrical work as source of energy to drive the reactionin the opposite direction.Content -6Electrolysis of Aqueous Salt Solution Using Inert ElectrodesLearning objectives:The students will be able to- Predict the products of electrolysis of an aqueous salt using inert electrodes.Understand the electrolysis of water.90

THE ELECTROLYSIS OF AQUEOUS NaClThe figure below shows an idealized drawing of a cell in which an aqueous solution ofsodium chloride is electrolyzed.Once again, the Na + ions migrate toward the negative electrode and the Cl - ions migratetoward the positive electrode. But, now there are two substances that can be reduced atthe cathode: Na + ions and water molecules.Cathode (-):Na + + e - Na E o red = -2.71 V2 H2O + 2 e - H2 + 2 OH - E o red = -0.83 VBecause it is much easier to reduce water than Na + ions, the only product formed at thecathode is hydrogen gas.Cathode (-): 2 H2O(l) + 2 e - H2(g) + 2 OH - (aq)There are also two substances that can be oxidized at the anode: Cl - ions and watermolecules.Anode (+):2 Cl - Cl2 + 2 e - E o ox = -1.36 V2 H2O O2 + 4 H + + 4 e - E o ox = -1.23 VThe standard-state potentials for these half-reactions are so close to each other that wemight expect to see a mixture of Cl2 and O2 gas collect at the anode. In practice, the onlyproduct of this reaction is Cl2.91

Anode (+): 2 Cl - Cl2 + 2 e -At first glance, it would seem easier to oxidize water (E o ox = -1.23 volts) than Cl - ions(E o ox = -1.36 volts). It is worth noting, however, that the cell is never allowed to reachstandard-state conditions. The solution is typically 25% NaCl by mass, whichsignificantly decreases the potential required to oxidize the Cl - ion. The pH of the cell isalso kept very high, which decreases the oxidation potential for water. The decidingfactor is a phenomenon known as overvoltage, which is the extra voltage that must beapplied to a reaction to get it to occur at the rate at which it would occur in an idealsystem.Under ideal conditions, a potential of 1.23 volts is large enough to oxidize water to O2gas. Under real conditions, however, it can take a much larger voltage to initiate thisreaction. (The overvoltage for the oxidation of water can be as large as 1 volt.) Bycarefully choosing the electrode to maximize the overvoltage for the oxidation of waterand then carefully controlling the potential at which the cell operates, we can ensurethat only chlorine is produced in this reaction.In summary, electrolysis of aqueous solutions of sodium chloride doesn't give the sameproducts as electrolysis of molten sodium chloride. Electrolysis of molten NaCldecomposes this compound into its elements.electrolysis2 NaCl(l) 2 Na(l) + Cl2(g)Electrolysis of aqueous NaCl solutions gives a mixture of hydrogen and chlorine gasand an aqueous sodium hydroxide solution.electrolysis2 NaCl(aq) + 2 H2O(l) ---------------- 2 Na + (aq) + 2 OH - (aq) + H2(g) + Cl2(g)Because the demand for chlorine is much larger than the demand for sodium,electrolysis of aqueous sodium chloride is a more important process commercially.Electrolysis of an aqueous NaCl solution has two other advantages. It produces H2 gas92

at the cathode, which can be collected and sold. It also produces NaOH, which can bedrained from the bottom of the electrolytic cell and sold.The dotted vertical line in the above figure represents a diaphragm that prevents the Cl2produced at the anode in this cell from coming into contact with the NaOH thataccumulates at the cathode. When this diaphragm is removed from the cell, theproducts of the electrolysis of aqueous sodium chloride react to form sodium hypochlorite,which is the first step in the preparation of hypochlorite bleaches, such asChlorox.Cl2(g) + 2 OH - (aq)Cl - (aq) + OCl - (aq) + H2O(l)Resource:http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch20/faraday.phpContent -7Electrolysis of a Molten Salt Using Active ElectrodesLearning objectives:The students will be able to- Predict the products of electrolysis of a molten salt using active electrodes.Electrolysis with Active ElectrodesIn an electrolytic cell external source of voltage is used to bring about a chemicalreaction. The electrochemical processes are of great importance in the laboratory and93

the chemical industry. For example, the process called electroplating involves usingelectrolysis to deposit a thin layer of one metal on another metal.Let's illustrate the principles of electrolysis with active electrodes by using the exampleof electroplating copper on a piece of steel.Figure below illustrates the electrolytic cell for our electroplating experiment. Theanode of the cell is a strip of copper metal and the cathode is the piece of steel that willbe electroplated. The electrodes are immersed in a solution of CuSO4(aq).Electrolytic cell with an active metal electrode. Copper dissolves from the anode to formCu 2+ (aq). At the cathode Cu 2+ (aq) is reduced and forms a copper "plate" on the cathode.At the anode we need to consider which substances can be oxidized. For the CuSO4(aq)solution, only the H2O solvent is readily oxidized. But the Cu atoms in the anode canthemselves undergo oxidation, the electrode reactions are as follows:Cathode (Steel plate):Anode (strip of copper):If we look at the overall reaction, it appears that nothing has been accomplished.However, during the electrolysis we are transferring Cu atoms from the Cu anode tothe steel cathode, plating the steel electrode with a thin layer of copper atoms.94

WORKSHEET-31. During the electrolysis of a molten salt (compound) the product at the cathode is:A. Non – metalB. MetalC. OxygenD. Chlorine2. During the electrolysis of a molten salt (compound) the product at the anode is:A. Non – metalB. MetalC. SodiumD. Magnesium3. During the electrolysis of a molten sodium chloride ( NaCl ) the product at theanode and the cathode are:Anode CathodeA. Sodium ChlorideB. Sodium chlorineC. Chlorine SodiumD. chloride sodium4. During the electrolysis of a molten lead iodide (PbI2 ) the product at the anodeand the cathode are:Anode CathodeA. hydrogen iodineB. iodine leadC. lead iodideD. lead iodine95

6. During the electrolysis of a concentrated (aq) CuSO4 the product at the cathode is:A. H2( g )B. O2( g )C. SO2( g )D. Red brown deposit Cu(s))7. During the electrolysis of a dilute (aq) CuSO4 the products at the cathode and theanode are:cathode anodeA. O2 ( g ) Cu(s)B. H2( g ) O2( g )C. Cu(s) O2( g )D. Cu(s) SO2( g )8. Which of the following does not contain ions?(a) Aqueous hydrogen chloride(b) Gaseous hydrogen chloride(c) Solid sodium nitrate(d) Molten sodium chloride9. Which of the following does not contain free ions?(a) Aqueous hydrogen chloride(b) Aqueous ammonia(c) Solid sodium nitrate(d) Molten sodium chloride96

10. When aqueous H2SO4 (aq) solution is electrolysed using inert carbon electrodes,the substance formed at anode is(a) hydrogen gas(b) Oxygen gas(c) Copper (II) ion(d) Copper deposit11. When aqueous H2SO4 (aq) solution is electrolysed using inert carbon electrodes,the substance formed at cathode is:(a) hydrogen gas(b) Oxygen gas(c) Copper (II) ion(d) Copper deposit12. When aqueous H2SO4 (aq) solution is electrolysed using inert carbon electrodes,the substance formed at anode is a:(a) Gas that burns with pop sound(b) Gas that relights a glowing splint(c) Brown gas(d) Pink solid13. The diagram shows the electrolysis of a molten compound X. What is compoundX?97

A. Copper (II) ChlorideB. Lead(II) bromideC. Sodium chlorideD. Sodium bromide14. Copper and hydrogen can each be formed by electrolysis. At which electrodesare these elements formed?15. Two elements X and Y form ionic compounds, XCl2 and Y2O3. The compoundsare separately melted and electricity is passed through the liquids. What are theproducts at the cathodes?98

A. chlorine and oxygenB. chlorine and YC. oxygen and XD. X and YContent-8The students will be able to- Describe applications of electricity in metallurgyUnderstand the metallurgy of aluminium from bauxite ore.Understand the method of refining copper using electrolysis.Understand the technique of electroplating.EXTRACTION OF ALUMINIUM:an ore of aluminium - BauxiteConcentration of ore-(a)Leaching of alumina from bauxiteLeaching is often used if the ore is soluble in some suitable solvent.The principalore of aluminium, bauxite, usually contains SiO2,iron oxides and titanium oxide(TiO2) as impurities. Concentration is carried out by digesting the powdered orewith a concentrated solution of NaOH at 473 – 523 K and 35 – 36 bar pressure.This way, Al2O3 is leached out as sodium aluminate (and SiO2 too as sodiumsilicate) leaving the impurities behind:Al2O3(s) + 2NaOH(aq) + 3H2O(l) → 2Na[Al(OH) 4](aq)The aluminate in solution is neutralised by passing CO2 gas and hydrated Al2O3is precipitated. At this stage, the solution is seeded with freshly prepared samplesof hydrated Al2O3 which induces the precipitation:2Na[Al(OH)4](aq) + CO2(g) → Al2O3.xH2O(s) + 2NaHCO3 (aq)99

The sodium silicate remains in the solution and hydrated alumina is filtered,dried and heated to give back pure Al2O3:Al2O3.xH2O 1470 K Al2O3(s) + xH2O(g)(b)Reduction of concentrated ore to pure metal –The concentrated ore willeventually be reduced (have its oxygen removed) by electrolysis of molten oxide,alumina (Al2O3). Since Alumina has a very high melting point (2045 ºC),themineral cryolite (Na3AlF6) is added to lower the melting point so that theelectrolysis may be carried out at about 950 ºC.The electrolytic cell has anode as carbon rod and cathode as carbon lining of thetank in which the electrolysis takes place. When current is passed through moltenalumina carbon dioxide is formed at the anodes, and aluminium at the cathode.Aluminium formed is heavier than the molten alumina/cryolite mixture, andsinks to the bottom of the cell, where it is tapped off. The procedure is known asthe Hall-Héroult process.100

ELECTROLYTIC REFINING OF COPPER:In this method,( When copper is first obtained by reduction of its ores, it is cast asimpure slabs or ingots, called blister copper) the impure blister ingots of metal is madeto act as anode. A strip of the same metal in pure form is used as cathode. They are putin a suitable electrolytic bath containing soluble salt of the same metal. The more basicmetal remains in the solution and the less basic ones go to the anode mud.The reactions are:Anode: M → Mn + + ne –Cathode: Mn + + ne – → MCopper is refined using an electrolytic method. Anodes are of impure copper and purecopper strips are taken as cathode. The electrolyte is acidified solution of coppersulphate and the net result of electrolysis is the transfer of copper in pure form from theanode to the cathode:Anode: Cu → Cu 2+ + 2 e –Cathode: Cu 2+ + 2e – → CuDuring electrolysis, copper passes into solution from the anodes, (leaving theimpurities, normally containing silver, gold and platinum) as an anode mud/slime,which sinks to the bottom of the cell. The anode reaction is101

ELECTROPLATING:Electroplating consists of depositing a thin layer of a metal on another, either forprotection or for the sake of appearance. Typically, a brass or nickel object is coatedwith a layer of silver by making use of electrolysis of a silver solution, using the objectto be coated as the cathode:The anode consist of pure silver, and the cathode is the object to be plated. Theelectrolyte is a mixure of silver nitrate with potassium cyanide.The reactions are:At the anode: Ag → Ag + + e -At the cathode: Ag + + e - → AgThe cyanide ensures a low concentration of silver ions, a condition for providing thebest plating results.During the process, the concentration of silver in the electrolyte remains constant, as therate of reduction at the cathode (which is the rate of deposition of silver on the object) isthe same as the rate of reduction at the anode (which is the rate of rate of dissolution ofthe silver anode).102

WORKSHEET-41. What are the positive electrodes in the cell made from?a. Aluminium,b. Carbon (graphite)c. Platinum,d. Steel,.2. During electrolytic reduction at which electrode is the aluminium formed?a. Anode (+),a. Cathode (-).3. Which half-equation describes how aluminium ions are discharged in the cell?a. Al + + e - → Al,b. Al 3+ - 3e - → Al,c. Al 3+ + 3e - → Al.4. Why do the anodes in the cell have to be replaced frequently?a. They get coated in a thick crust of solid aluminium oxideb. They melt in the high temperature inside the cell,c. They are burned away by oxygen reacting with the carbon to form carbondioxide gas,d. The aluminium is formed on them which has to be removed.5. Why is molten cryolite added to dissolve the aluminium oxide in an electrolyticcell?a. To increase the melting point of the electrolyte,b. To increase the resistance of the electrolyte,c To make the electrolyte richer in aluminium,d. To lower the melting point of the electrolyte.103

6. From which ore is aluminium metal extracted?a. Chalcocite,b. llmenite,c. Bauxite,d. Haematite.7. Which aluminium compound is electrolysed in the extraction of aluminium?a. Aluminium bromide,b. Aluminium fluoride,c. Aluminium oxide.8. Look at the diagram in figure of the cell used in the extraction of aluminium, thenmatch the letters to the correct labels.a. ________________________b. _________________________c. ________________________d. ________________________104

Watch this video on animation of a galvanic cell-http://www.youtube.com/watch?v=nNG5PMlHSoA&feature=relatedUse appended power point presentation on electrochemical cells-DiscoveringElectrochemical CellsPost Content-1Electrochemical Theory of RustingThe Students will be able to-Describe rusting of iron as an electrochemical reaction.Device methods of preventing rusting using the concept of electrochemistry.CorrosionThe process of slowly eating away of the metal due to attack of the atmospheric gaseson the surface of metals; forming oxides, carbonates, sulphides is called corrosionCorrosion slowly coats the surfaces of metallic objects with oxides or other salts of themetal. The rusting of iron, tarnishing of silver,development of green coating on copperand bronze are some of the examples of corrosion. It causes enormous damage to105

uildings, bridges, ships and to all objects made of metals especially that of iron. Welose crores of rupees every year on account of corrosion. In corrosion, a metal isoxidised by loss of electrons to oxygen and formation of oxides.FACTORS WHICH AFFECT CORROSIONThe factors which affect corrosion are:(i) Reactivity of the metal : The more active metals are prone to corrosion .(ii) Presence of impurities : Presence of impurities helps in setting up anelectrochemical cell and makes the corrosion to occur rapidly. For example,pure iron does not rust.(iii) Air and moisture : Air and moisture are quite helpful in corrosion. Thepresence of gases like CO2 and SO2speeds up the process of corrosion. Forexample no rusting is caused if iron is kept under vaccum.(iv) Strains in metal:causes corrosion to take place faster. For example, in ironarticles, rusting is more pronounced on the areas having bends, scratches, nicksand cuts.(v) Presence of electrolytes : The presence of electrolytes helps in setting of anelectrochemical cell and make the corrosion process faster. For example, ironrusts more rapidly in saline water in comparison to pure water.Rust-Corrosion of ironELECTROCHEMICAL THEORY OF RUSTINGRust is the chemical produced when iron compounds corrode in the presence of oxygenand water. It is a mixture of iron oxides and hydroxides.. Corrosion of iron (commonlyknown as rusting) occurs in presence of water and air. The chemistry of corrosion isquite complex but it may be considered essentially as an lectrochemical phenomenon.At a particular spot of an object made of iron, oxidation takes place and that spotbehaves as anode and we can write the reaction106

Anode: 2 Fe (s) → 2 Fe 2+ + 4 e –E 0 Fe2+/Fe= – 0.44 VElectrons released at anodic spot move through the metal and go to another spot on themetal and reduce oxygen in presence of H + (which is believed to be available fromH2CO3 formed due to dissolution of carbon dioxide from air into water. Hydrogen ionin water may also be available due to dissolution of other acidic oxides from theatmosphere). This spot behaves as cathode with the reactionCathode: O2(g) + 4 H + (aq) + 4 e – ⎯→ 2 H2O (l )E 0 H + /O 2 /H 2O =1.23 VThe overall reaction being:2Fe(s)+O2(g) + 4H + (aq) ⎯→ 2Fe 2 + (aq)+ 2 H2O (l )E 0 cell =1.67 VThe ferrous ions are further oxidised by atmospheric oxygen to ferric ions which comeout as rust in the form of hydrated ferric oxide (Fe2O3. x H2O) and with furtherproduction of hydrogen ions.Prevention of RustingPrevention of corrosion is of prime importance. It not only saves money but also helpsin preventing accidents such as a bridge collapse or failure of a key component due tocorrosion.(i)Barrier protection107

One of the simplest methods of preventing corrosion is to prevent the surfaceof the metallic object to come in contact with atmosphere oxygen and moisture.This can be done bycovering the surface with paint or oil or grease or by some chemicals (e.g.bisphenol).covering the surface by other metals (Sn, Zn, etc.) that are inert or react tosave the object.(ii)(iii)Sacrificial protectionThus sacrificial Protection involves-Covering the surface with a more electropositive metal than Fe. The more electro positive metal loses electrons and aslong as this coating is present Fe is protected.Zinc is commonly used to coat ironsurfaces. The process of coating a thin film of zinc on iron is known asgalvanisation . Since zinc is more electropositive than iron, it loses electronspreferentially and goes into solution as Zn 2+ ion. As long as zinc is present on thesurface, iron will not corrode. If some scratches occur on the protective film ofzinc, both iron and zinc are exposed to oxygen. But due to the lower reductionpotential of Zn compared to that of iron, zinc undergoes oxidation in preferenceto Fe. Thus, iron does not corrode even if the film of zinc is broken at some point.Electrical protection (Cathodic protection)An electrochemical method is to provide a sacrificial electrode of another metal(like Mg, Zn, etc.) which corrodes itself but saves the object.This method is used for protecting iron articles which are in contact with watersuch as underground water pipes. The article of iron is connected with moreactive metals, like magnesium or zinc, either directly or through a wire. Fe acts asthe cathode and the more reactive metal as the anode. Consequently, the activemetal loses electrons in preference to iron and therefore, protects iron from beingrusted .108

Example: Fe can be connected to Mg, Zn or Al which are called the sacrificialanodes. Used for protecting under ground pipes from rusting.Video for electrochemical theory of rustinghttp://www.youtube.com/watch?v=OdMBczqhPWoPost content-2Fuel CellsProduction of electricity by thermal plants is not a very efficient method and is a majorsource of pollution. In such plants, the chemical energy (heat of combustion) of fossilfuels (coal,gas or oil) is first used for converting water into high pressure steam. This isthen used to run a turbine to produce electricity. We know that a galvanic cell directlyconverts chemical energy into electricity and is highly efficient. It is now possible tomake such cells in which reactants are fed continuously to the electrodes and productsare removed continuously from the electrolyte compartment. Galvanic cells that aredesigned to convert the energy of combustion of fuels like hydrogen, methane,methanol, etc. directly into electrical energy are called fuel cells.One of the most successful fuel cells uses the reaction of hydrogen with oxygen to formwater.109

The cell was used for providing electrical power in the Apollo space programme. Thewater vapours produced during the reaction were condensed and added to thedrinking water supply for the astronauts. In the cell, hydrogen and oxygen are bubbledthrough porous carbon electrodes into concentrated aqueous sodium hydroxidesolution. Catalysts like finely divided platinum or palladium metal are incorporatedinto the electrodes for increasing the rate of electrode reactions. The electrode reactionsare given below:Cathode: O2(g) + 2H2O(l ) + 4e – → 4OH – (aq)Anode: 2H2 (g) + 4OH – (aq) → 4H2O(l) + 4e –Overall reaction being:2H2(g) + O2(g) → 2 H2O(l )The cell runs continuously as long as the reactants are supplied.Fuel cells produceelectricity with an efficiency of about 70 % compared to thermal plants whose efficiencyis about 40%. There has been tremendous progress in the development of new electrodematerials, better catalysts and electrolytes for increasing the efficiency of fuel cells.These have been used in automobiles on an experimental basis. Fuel cells are pollutionfree and in view of their future importance, a variety of fuel cells have been fabricatedand tried.110

Rubrics of Assessment for LearningUnit 3, Electricity and ChemistryParameterBeginning(0)Approaching(1)Meeting(2)Exceeding(3)Student is able to describeoxidation reduction in termsof electron gain or loss ofoxygen or hydrogen.Student is able to describehow electrolytic cells workStudent is able to predict theproducts of electrolysis ofmolten salts using inertelectrodesStudent is able to predict theproducts of electrolysis ofaqueous solutions ofelectrolytes using inertelectrodesStudent is able to predict theproducts of electrolysis ofaqueous solutions ofelectrolytes using reactiveelectrodesStudent is able to apply theknowledge of electrolysis inrefining of metals like copper.Student is able to apply the111

understanding of electrolysisin electroplatingStudent is able to apply theknowledge of electrolysis toextraction of Al from bauxite.Student is able to relaterusting of iron toelectrochemical theoryStudent is able to suggestmethods of prevention ofrustingStudent is able to describeworking of Electrochemicalcells-simple Zn/Cu cellsStudent is able to sketch andlabel electrochemical cells.112

Suggested Video Clips /Web Links / PowerpointsPower point-1Redox reactionVideo clip-1galvanic cellhttp://www.youtube.com/watch?v=nNG5PMlHSoA&feature=relatedVideo clip-2 Zn-Cu galvanic cellhttp://www.youtube.com/watch?v=0oSqPDD2rMA&feature=relatedVideo clip-3 Electrolysishttp://www.youtube.com/watch?v=lVK8RxkmOechttp://www.youtube.com/watch?v=xEZtSfBtZScVideo clip-4 electrochemical theory of rustinghttp://www.youtube.com/watch?v=OdMBczqhPWoResourceshttp://www.funsci.com/fun3_en/electro/electro.htmhttp://chs.carlsbadusd.k12.ca.us/kistler/renew/unittests2/electst.htmhttp://chemed.chem.purdue.edu/genchem/topicreview/bp/ch9/redox.phphttp://www.chemguide.co.uk/inorganic/redox/oxidnstates.htmlhttp://www.saskschools.ca/curr_content/chem30/modules/module8/lesson1/lspont.htmlhttp://chemed.chem.purdue.edu/genchem/topicreview/bp/ch9/redox.phphttp://misterguch.brinkster.net/pra_equationworksheets.htmlhttp://www.saskschools.ca/curr_content/chem30/modules/module8/lesson3/labelectrolysis.htmhttp://chemed.chem.purdue.edu/genchem/topicreview/bp/ch20/faraday.phphttp://www.woodrow.org/teachers/ci/1986/exp28.htmlhttp://www.physchem.co.za/OB12-che/electrolysis.htm#aluminiumhttp://www.authorstream.com/Presentation/nandakumargoud-130808-redoxreactions-reduction-oxidation-education-ppt-powerpoint/http://www.tutorvista.com/content/chemistry/chemistryiv/electrochemistry/corrosion.php113

UNIT 3:How do organisms reproduce? (Class X)CoreExtensionSYLAll living organism‘sreproduceOffspring resembles parentsFamily PlanningSexually transmitted diseasesLABUAsexual reproductionVegetative PropagationSexual reproduction in plantsSexual reproduction in HumanbeingsSafe sex vs HIV/AIDSChild bearing and woman‘shealthSFertilization114

MatrixContent Skill Intended learningAll livingorganismreproduceOffspringsresembleparentsAsexualreproductionVegetativeReproduction inplantsDeduceExtrapolateDemonstrate, Analyse, Identifyand SummariseExplain, Draw, Identify,Compare, Contrast, Describe,Examine, summarizeDefine, Explain, Draw, Identify,Compare, Contrast, Describe,Differentiate, Examine,summarize Recognize the need forreproduction Understand thatreproduction involvesparent/s Assess that the offspringresemble parent/s Summarize the variousmodes of asexualreproduction Define vegetativereproduction (orpropagation) in plants List the specializedplant structures whichhelp in vegetativepropagation. anddescribe their general,morphology withexamples.Name and draw roots,stems and leaves, etc,specialized forvegetative propagation.Differentiate between115

natural and artificialways of vegetativepropagation.Differentiate betweencuttings, layering, andgrafting by givingexamples.Define micropropagation anddescribe methodsemployed in it.State advantages ofmicro propagation.Asexual andSexualReproductionCompare, Contrast,Differentiate,Comprehend Describe the advantagesof vegetativepropagation. Understand thesignificance of Asexualand Sexual Reproductionoperating in nature. Compare andcontrast two types ofreproduction foundin natureImportance ofsexualreproductionComprehend, Deduce, Explain Understand the need ofsexual reproduction Learn that variations,which arise during116

SexualreproductionIn plants-ISexualreproductionIn plants-IISexualreproductionIn AnimalsFertilizationIdentify, Relate, DrawComprehend, explain, Justify,DescribeDescribe, Comprehend, DeduceCompare117sexual reproduction, areimportant because theyallow survival of speciesand they lead toevolution Comprehend thatVariations in nature arerandom. Both positiveand negative variationsmay occur. However,only positive orbeneficial variations areretained. the negativevariant is gradually lostfrom the gene pool. Identify structure andfunction of the variousparts of a flower Understand the stagesand componentstructures involved inthe process ofreproduction in plants. discuss the process offertilization in plantsidentify the structureand function ofreproductive organs inhuman male and female.

Post Contentdescribe the process ofreproduction anddevelopment includingfertilization.Family Planning Relate, Explain, Comprehend • The students willunderstand the need forfamily planning andvarious ways to conductthe same.SexuallytransmitteddiseasesDescribe, Explain, Compare The students willbecome aware of thesexually transmitteddiseases and learn howcan they be prevented.HIV/AIDS Relate, Comprehend, Explain Identify some of thesensitive issuesconnected withpreventing, acquiring,and coping withHIV/AIDSExamine personalknowledge in terms ofwhat they already knowand what they want toknow.Consider howHIV/AIDS affects many118

more people than itinfectsChild bearingand women’shealthRelate, Explain, Comprehend explain the adverseeffects of child birth onthe female anatomy.They would becomesensitive for thewomen‘s health.119

Scope DocumentUNIT 3: How do organisms reproduce?All living things eventually die, but the species to which they belong can survive formuch longer than a single lifetime because of reproduction. Reproduction is acharacteristic feature of all living organisms. It involves the creation of organelles,cells, or organisms of the same kind. It adds new organisms to the population, andthus helps to compensate for the inevitable death of individual members.Learning outcomes - FoundationAt the end of this unit students should be able to:Recognize the need for reproductionUnderstand that reproduction involves parent/s and the offspring resembleparent/sDuring asexual reproduction, offspring resemble parentSummarize the various modes of asexual reproductionExplain how do plants exhibit asexual reproductionUnderstand the need of sexual reproductionLearn that variations, which arise during sexual reproduction, are importantbecause they allow survival of species and they lead to evolutionComprehend that Variations in nature are random. Both positive and negativevariations may occur. However, only positive or beneficial variations areretained. the negative variant is gradually lost from the gene pool.Identify the various parts of the flowerUnderstand the stages and component structures involved in the process ofreproduction in plants.discuss the process of fertilization in plantsLearn, in detail, the Structure And Functions Of The Human ReproductiveSystem120

Learning outcomes – ExtensionAt the end of this unit students should be able to:Understand that during reproduction, the information for inheritance ofcharacteristics is passed on from the parents to the offsprings in the form ofDNA.Explain the structure of DNAIdentical and Fraternal TwinsLearn that the hybrid plants are propagated through budding and the processof tissue cultureSummarize what are sexually transmitted diseases and that how they spreadfrom one person to another while having sexUnderstand the importance of contraceptive methodsDiscuss safe sex vs HIV/AIDSComprehend that the health of child bearing women is of utmost importanceCross Curricular links:English: The students can build up the vocabulary words. They can spin a story onsexual and asexual reproduction highlighting the differences between them.Debate on cancer- the Uncontrollable MitosisParagraph writingMath: Data handling, pie chart of survey on diseases.ICT: Power Point presentations on types of asexual ReproductionArt & Craft : Making models of mitosis and meiosis using a variety of materials121

Teachers’ NotesActivity-1Need for ReproductionTeacher will make students play Snake and ladder game with specific instructionsthat Snakes would represent ―no reproduction‖ and ladders represent―reproduction‖ to help them understand and deducereproduction in a population of living organisms.the significance ofIn order to help students understand the concept , appropriate questions may beframed and given to students to answer. Care may be taken while framing questionsthat child should be able to answer them on his/her own words. The initialquestions may be framed to recall (Knowledge-easy type)and subsequent questionsmay gradually become complex (Application,analysis and synthesis). Whilesearching for answers ,this helps students to slowly and gradually analyse theactivity and build up knowledge. Students get the feel to have discoveredknowledge on their own.Activity-2Offsprings Resemble ParentThe intent of this activity for students is to recognize that cell division is a complexprocess and it is essential to the survival i.e. growth or reproduction of all livingbeings. The process of cell division occurs perfectly almost all of the time.This activity covers the cell division Mitosis as a process to promotegrowth/reproduction. To facilitate the students' understanding of the phases ofmitosis, microscopes and prepared slides of mitosis (either plant or animal cells)may also be used.122

Students should recognize the nucleus as the control centre of the cell and DNA asa chemical involved in genetic traits. Students already know cell division and cellcycle as they have studied it in Unit 2 Class-IX. This would be a recapitulation ofthe concept of cell division which is fundamental to understand life.2.1 Student Activity(Additional activities for teacher to use as and when required)Students will discuss and make notes on DNA(chromosome),the importance of accuracy in copying the DNA(chromosome) during celldivision and the final outcome of two genetically identical daughter cells.The teacher will direct theo brief discussion ando note making activity.2.2 Student Activity: Students may use materials such as wool to demonstratethe changes in DNA(Chromosome) while cells undergo mitosis. They willcomplete their recording sheet from Activity 2.1 to outline the majorchanges to the DNA (chromosome) during mitosis. The appearance anddisappearance of the relevant structures inside the cell during this processshould also be noted.The teacher will monitor the completion of the recording sheet and helpstudents use wool to demonstrate the extended DNA in interphase and thecondensed DNA in prophase.123

2.3 Student Activity:Student Activity: Working in groups, students will be given a set oflaminated cut-outs of diagrams showing the individual stages of mitosis.The cut-outs are unlabelled. Students will be asked to hold them in theirhands and take position in order from first to last as per the positionmentioned in the mitosis chart .Each of them would state their reasons fortheir position in that order and what they believe the process represents.Smaller cut-outs should then be attached on a recording sheet in a circle toshow that the process is a cycle.Activity-3Asexual ReproductionThe purpose of this activity is to clarify that asexual reproduction produces singleparentoffspring. Students will use yeast (unicellular fungus) and Spider plants(multicellular) to demonstrate budding and vegetative propagation the laboratory.Students will also draw and learn about five different types of asexual eproductionAsexual reproduction is common in the plant and animal kingdoms, but oftenoverlooked by teachers and students. This lesson helps students understand andremember asexual reproduction by providing a wide range of common examples. Italso provides an opportunity for students to grow asexual propagates in thelaboratory, providing a lasting memory of the experience.Teacher need to explain varieties and the significance of alternation of generations inthe life cycle of different organisms.124

Vegetative propagation takes several weeks to demonstrate. You may want to beginthe preparation for experiment weeks before the lesson. Teacher must providestudents record sheet for periodic observations of the propagates.3.1 Student Activity :Some examples of Asexual ReproductionMaterial :Plastic bags, journal, petri dish, potato, spider plant or geranium,sugar, toothpicks, yeast, microscope slide, light microscope125

Procedure : Any Type ofDescriptionof the followingexamples could beused in the sciencelaboratory toreinforceOrganismAsexualReproductionBacteria, Amoebe Fission Many bacteria and unicellularorganismseproduce through binary fissionSpider plant,water hyacinthVegetativePropagationIt also produces branched stolons with smallwhite flowers and baby plantlets. These can beplaced in r soil to produce another plant. Spiderplants also reproduce sexually.Strawberries.Grass VegetativePropagationRunners are offshoots of the parent plant, Atintervals along the runner, nodes appear. Fromeach node, a "daughter plant" can develop,complete with roots and leaves. Strawberriesalso reproduce sexually.flatworms Fragmentation Some flatworms like Plannaria can grow by celldivision from a fragmented section of its body.Paramecium Fission Paramecium is a single-celled organism thatreproduces by splitting in two.MintVegetativePropagationThis is a stolon, it put out roots at the nodes.When the stolon is broken, or part of it dies, theshoots become independent plants.Hydra Budding Cell division forms a bud that grows in to anidentical copy of its single parent.It laterseparates from the parent and becomesindependent.126

Teacher may take precautions as growing plants in the classroom may exposestudents to mould and mould spores. Check with students and their parents toensure that no student has a known mould allergy before beginning theexperiments. If students have mould allergies, Do Not conduct this experimentAsk students to explore other types of asexual reproduction on the Internet.Ask students to carry out an experiment each to see who can produce themost offspring from a potato, geranium,spider plant or any other vegetativeparts within a given fixed period of two-three months.Activity-4Vegetative Reproduction in plants-Vegetative propagation. Teacher will organisetwo activities. First activity is to provide hands on experience and the second is ademonstration to help students know more about variety of vegetative propagationbeing adopted by plants they are familiar with, in the nature around them.Teacher will direct the brief discussion and note making activity.Man has the ability to be resourceful and enterprising. He has manipulated thenatural ability of the vegetative propagation to increase the production of plants asseen in the industry of Floriculture, Horticulture and Agriculture.Teacher may take precautions as growing plants in the classroom may exposestudents to mould and mould spores. Check with students and their parents toensure that no student has a known mould allergy before beginning theexperiments. If students have mould allergies, Do Not conduct this experiment127

Activity: 5Asexual and Sexual ReproductionTeacher will ask students to sit in pairs and discuss and contemplate on thesignificance of each type of reproduction and also tell them that it is okay if theyrepeat what the first person said but they also need to think of new information toshare.Teacher may ask few interesting questions in between to help sustain interest of thestudents. A worksheet with relevant progressive information seeking questions canbe prepared by the teacher and given to the students to reinforce the learning. It mayappear to some of us as time consuming for students yet it has its own advantage indisguise. One, it saves paper, it is an alternative to routine task and the studentsdevelop ability to observe and note the information carefully.Learning FramesPurpose: To increase the level of comprehension by focusing student learningwithin a controlled contextDescription: Learning frames are a sequence of spaces connected by key languagewords to help students focus their learning. The purpose is threefold: 1) to provide aframework or direction to guide students' understanding and responding; 2) to givea structured format to follow for engaging in a writing activity; 3) to help studentsdevelop independent comprehension strategies.Procedure:1. Display a transparency of the Learning Frame on an overhead screen .Explain to the students that this frame, like the frame of a new house in a128

picture, will allow them to fill the blanks with information from what theyjust learned about different modes of reproduction..2. Model the Learning Frame by filling in the frame using information learned3. Read the frame aloud.4. Next, pass out a blank Learning Frame to each student.5. Allow students to fill out their Learning Frames in a manner which reflectswhat they learned from the day's class lesson.Activity-6Importance of Sexual ReproductionTeacher will explain Crossing Over by recapitulating the knowledge students hadlearnt in Unit-2 of Class-IXWhen pairs of chromosomes come together during meiosis- 1, they exchange somegenetic material.The exchanging of genetic material between chromosomes is called crossing over.This is why sexual reproduction results in genetic variability. For example, brothersand sisters can have different hair color.Here is a summary of how crossing over occurs:1. Chromosome pairs line up side by side during early prophase 1. At this stage,each chromosome is made up of two identical strands (chromatids) heldtogether at the centromere.2. The pairs of double-stranded chromosomes twist around each other. Breaks inthe strands of each chromosome reattach to strands from the pairedchromosome. The point where crossing over occurs is visible as an X-shapedstructure.129

3. Spindle fibers attach to one side of each centromere during metaphase 1. As thechromosomes are pulled apart during anaphase 1, the points where thechromosomes cross over separate. Each chromosome takes a small piece of newgenetic material with it.Note: Student activity 6.1 is a simple hands –on activity for students to recall andunderstand how chromosomes cross over during Meiosis-1 while crossing overprocess. They have already studied in class-IX, Unit-2.This warm-up activity willhelp students to carry out Role Play more effectively,i.e.Activity 6.2Student Activity:1 (Additional activity for teacher to use as and when required)Working in groups, students will be given a set of laminated cut-outs of diagramsshowing the individual stages of meiosis. The cut-outs are unlabelled. Students willbe asked to hold them in their hands and take position in order from first to last asper the position mentioned in the meiosis chart. Each of them would state theirreasons for their position in that order and what they believe the process represents.Smaller cut-outs should then be attached on a recording sheet in a circle to show thatthe process is a cycle.They will complete their recording sheet to outline the major changes in the DNAduring meiosis.The appearance and disappearance of the relevant structures inside the cell duringthis process should also be noted.130

Activity-7Sexual Reproduction in Plants-IThe Structure and Functions of FlowersWhile showing audio-Video films ,teacher may provide real flowers (One of eachkind like regular and irregular shape, Complete and incomplete flower, in thegroup of five students.) along with required apparatus (Watch Glass, Slides,Forceps and Dissecting Microscope) and ask students to identify parts of the floweras directed in the film. The hands-on experience will help students relate theirknowledge of flower with variety of flowers of any shape and size in future whenthey come across any such situation.Teacher may prepare an appropriate worksheet to reinforce the learning.Activity-8Sexual Reproduction in Plants-IIPollination and FertilizationTeacher may explain details of the types of pollination and the process offertilisation with the help of a chart in the class to be followed by the Audio-VideoActivity.Some extra information about Development of pollen grains and embryo sac is givenhere for teacher‘s information in case students are curious to know about it.The sex cells of the flowering plant are called gametes. There are both male andfemale gametes thus the flower undergoes sexual reproduction.Teacher may help students appreciate the variety of mechanisms operating atdifferent stages of plant life cycle and in nature to facilitate sexual reproduction in131

plants resulting in inheritance of characters and yet giving rise to variety, which isthe essence of sustenance of life on this planetActivity 9A:To teach male reproductive system, the teacher may inform about it to the parents.Encouraging parent and child communication at home will make students morecomfortable in the classroom, and also will help to avoid any conflicts with parents.The teacher may explain using a video, slides or models. A guest speaker referably adoctor can be invited to discuss this topic. Children should be encourages to askquestionsWord SearchWord searches are commonly found in daily newspapers and puzzle books. Someteachers use them as educational tools for children, the benefit being that youngminds can learn new words and their spellings by intensively searching for them,letter by letter, in the puzzle.132

Activity 9 BThe female reproductive system can be taught using a model, chart or a power pointpresentation. A separate class for girls may be conducted to encourage girls to cleartheir queries.Sexuality is not only about biology and science, but also about social, emotional, andbehavioural differences that occur throughout life.The teacher may ask the students to write their queries on a paper and hand it over.The teacher may then clear them on the following day.Activity 10Students are reminded human system. Example: Respiration system, nervoussystem, reproduction system, and etc.Students are asked menstruation cycle. They can be shown a video followed by apeer discussion. A panel can be made and the students are given sub topics offertilization. They will then be able to answer questions put up by their peers.An animation or a video may be shown to show the process of fertilization.The kids may then research on related topics like abortion and ectopic pregnancy.133

Activity 11The teacher may discuss the need of family planning to begin the class. She needs tohave the ability to impart confidence, compassion, understanding and friendliness.The teacher may discuss different types of family planning or birth control methods:a. Condomb. Spermicidesc. Diaphragm or cervical capd. Birth control pillse. Hormone Injectionsf. Skin patchg. Vaginal ringh. Intra-uterine device (IUD)i. Natural family planning (calendar method)The students after becoming aware of the need for family planning may designposters to raise awareness in the local community.Activity 12The purpose of teaching the concept is to get students to think about and becomeinformed about various sexually transmitted diseases. Students will not only learnabout different STDs but also get practice giving a presentation to the class. Byhaving students thoroughly research one STD, and then sharing the importantinformation to the class, this provides the important information found throughoutthe research process, without having students research each STD on their own.Also, having students present their topic to the class, gives them practice withpresentation skills. Presentation skills are not only important for education, buteveryday life as well.134

Activity 13The topic of AIDS can be dealt in various ways. Using the media is a powerful wayof reaching large numbers of young people with HIV and AIDS information andprevention messages. The students may be encouraged to make advertisements,raps, short fils to raise awareness in the community. Peer education is a particularlyeffective way of targeting difficult to reach groups, such as young people who donot attend school, with vital AIDS education. Effective AIDS education encompassesboth scientific and social aspects of HIV and AIDS. Knowledge of the basic science ofHIV and AIDS is important for understanding how the virus is passed on and how itaffects the body Developing life skills and discussing matters such as relationships,sexuality and drug use, are fundamental to AIDS educationActivity 14The teacher may invite a guest speaker to discuss the importance and various waysof family planning. The students may conduct a community walk carrying slogansand banners to convey the message. The students may also prepare a questionnaireto conduct a survey of people using family planning methods.Activity-1 Need for reproductionLearning OutcomesAfter completing the activity the students will be able toRecognize the need for reproduction135

STUDENTTEACHERSUPPORTMATERIAL(TSSM)136

Content: ReproductionAll living organisms during their life time follow a life cycle-i.e. they are born, theygrown, and they eventually die. For example, larvae are born, they grow intobutterfly, and they eventually die. In order to prevent the Species to disappear/ dieout from this planet/ an ecosystem, all living things reproduce. Reproduction is theprocess by which copies are made. To reproduce means to make again or to copy.Unlike Xerox copies, the nature of copying in living organisms show a range. It maybe exact, similar or a variable copy.Growth in the living being takes place because the cells in their bodies divide/reproduce themselves. Sustainability of life is also because of the same reason. Forexample, some skin cells are constantly reproducing themselves while other skincells are dying. As a persongrows , the skin cells reproduce faster than they die. Thesame principle is applied to bone cells and other tissues. Bone cells and other tissuesare constantly reproducing. A person grows taller when their bone cells arereproducing at a faster rate than rate at which they are dying. When a personbecomes an adult, the bone cells reproduce relatively slowly. As a result, dead bonecells are replaced slowly, that is the reason why adults do not continue to grow tallerand taller.Organisms reproduc through different ways. Plants reproduce by producing seeds.Mushrooms have spores to reproduct. Some animals, like hen reproduces by layingeggs. Mainly there are two types of reproduction found in organisms: sexualreproduction and asexual reproduction.―Asexual‖ means non-sexual. Asexual reproduction takes place without involvingmales and females. In this of reproduction, an organism makes copies of itselfthrough Mitotic cell division. Many Monerans and protists reproduce byasexualmode of reproduction. One of the mode of reproduction is by fission, which meanssplitting. In other words, after duplicating their genetic material, the body of theseorganisms split in half to create two organisms from one. This enables them to grow137

and reproduce very quickly.Some fungi, like moulds, mushrooms, and mildews, also reproduce asexually. Theyreproduce by forming spores in large quantity. Spores are typically single cells thatare often protected by a hard covering. Spores detach from the parent organism andgerminate in a new location to become a new organism.Yeast, on the other hand, reproduces asexually through budding. In budding, a budis formed on one side of the cell. It eventually breaks off and forms a new yeast cell.Asexual reproduction is also used by some plants and animals in a process calledregeneration. Regeneration means to make or generate again.. One of the mostfamiliar examples of plant regeneration is called cloning. In cloning, a leaf, stem orroot is detached from the main plant. This piece of the plant is then put into moistmaterial. As a result, it grows and a new plant is formed. Garden plants, like roses,Jasmine are often reproduced by cloning.Other animals, like starfish, have much greater ability to regenerate.,If theamputated arm has a piece of the center of the starfish, the lost arm can also growinto a new starfish. Flat worms also have greater regenerative capabilities. When aflat worm(Plannaria) is cut in half, both halves regenerate to form new worms.138

Student ActivityStudents can be made to understand the concept of ―Need for Reproduction‖ moreclearly by playing the game Snake and ladder.Material required:Snake and ladder gamePlane sheet and pencilInstructions:This activity (game) may be carried out in groups.Each group may have4-8 students.2-4students may be allowed to play the game simultaneously using differentcolour (Each colour represent population of a species) tablets.With every player there must be a student to keep a count ofincrease/decrease in the number of population.Procedure:Start the game of snake and ladder. Snakes would represent ―no reproduction‖ and ladders represent―reproduction‖.Two-four tablets (as per the number of players) represent populations of two–four different SpeciesIdentify the population of each species with a specific colour and start thegame.Consider every climb of the ladder as an addition to population. Count thenumber of times you go up.Consider every bite of the snake and going down as losing the members fromthe population.Keep a count of it.139

Based on the observations, answer the followingQ.1 What happens to the Species population when they are bitten by the Snakes?Q. 2 What happens to the species population when they get to the foot of aladder?Q.3 What happens if the population is more frequently bitten by the snakesi. e. No reproduction ?Q.4 Explain the significance of ladder in the game /importance of reproduction ina population?Q.5 Describe the concept of reproduction as an essential life process.Q.6 Why must organisms reproduce? Why don‘t they just live forever?Q.7 What would eventually happen to a species if every member suddenly losesits ability to reproduce?140

Worksheet-1Multiple Choice:1. Development of a plant from any vegetative part isa. Cell divisionb. Pollinationc. Vegetative reproductiond. Fertilization.2. Garden plants, like roses, are often reproduced by:a. Seedsb. sexual reproductionc. cloningd. budding3. Yeast reproduces asexually through a process called:a. Spore formationb buddingc. binary fissiond. binding4. In Hydra asexual reproduction takes place with the help ofa. Spore formationb. Fragmentationc. Buddingd. Binary fission.141

True or False :_________5. All living things have a life cycle- they are born, they grown, and theyeventually die._________6. Some animals, like chickens, reproduce by fragmentation._________7. To reproduce means to make a copy._________8. The less complex an animal is, the more complex the ability toregenerate becomes._________9. Humans grow because the cells in their bodies reproduce themselves.Activity-2Offsprings Resemble ParentLearning OutcomesUnderstand that reproduction involves parent/sExplain that the offspring resemble parent/sContent : Off springs and Parents look similar.DNA (Deoxyribonucleic acid) is the genetic material found in the chromosomes inall the living organisms, which may be are present in the nucleus of every cell of aliving body in case of eucaryotes and in case of prokaryotes it is not bound in a nucleus..The DNA carries the information for making proteins and is responsible formaking variety of proteins.Proteins are the building block of body of an organisms.Each specific type of protein leads to a specific type of body design.Thus, it is the DNA molecule that is responsible for the specific body design of an142

individual. Therefore, it may be concluded that the DNA needs to be transferredfrom parents to off springs in order to makes them look similar/inherit similarcharactersDNA Protein body structureDNA is responsible for different body structuresStudent ActivityRole Play: Students will perform an act to depict Mitosis where chromosomes split,reorganise and replicate in daughter cells. Chromosomes in daughter cells areidentical as parent cell and hence give same characteristics to daughter cells.Material required:ChalkDusterCD-ROM or videos showing the stages of mitosisFour different coloured Kite paperChart showing stage of Mitosis143

Instructions:Before the Role play, students may be allowed to view a moving sequence ofmitosis using websites, ,videos or chart. In groups of 8, students will enact theprocess of mitosis where two students will represent a pair of chromatids of echromosome. Add more students (if required) to show replication of chromatids indaughter cellProcedure:An out line of the cell may be drawn with the help of a chalk on the floor.Nuclear membrane /Cell membrane may be drawn or removed w ith thehelp of a chalk and a duster respectively (as and when required).This particular cell has 4 chromosomes.Each pair of students represent a pair of chromatids of a chromosome. Twostudents representing a pair of chromatids may cover their sleeves wih oneparticular colour kite paper indicating identical nature.Use four colours to represent four chromosomes.Enact the movement of chromosomes in different the stages of mitosis one byone. Later students can do a self- or peer- assessment for the activity theyhave just performed to assess how well their skit reflected the events of mitosisshown in the video. .Www.Lessonsnips.com144

Worksheet-2Answer the followingQ.1 Is DNA content different in daughter cells from that of parent cell, producedas a result of Mitosis?Q.2 Do daughter cells produced as a result of Mitosis resemble the parent cell?Q.3.Which kind of cell division is involved in asexual reproduction?Q.4 How would the characteristics of an asexually produced offspring relate toits parent? Write in your own words.Q.5 How many parent/parents are required to be involved in asexualreproduction?Q.6 Name two plants and two animals which reproduce through asexual mode ofreproduction?145

Activity-3Asexual ReproductionLearning Outcomes• Summarize the various modes of asexual reproductionContent.:Asexual reproduction is a mode of reproduction by which an offspring arise from asingle parent and inherit the genes of that parent only, it is reproduction which doesnot involve meiosis, ploidy reduction, or fertilization. A more stringent definition isreproduction without the fusion of gametes. Asexual reproduction is the primaryform of reproduction for single-celled organisms such as the archaea, bacteria, andprotists. Many multicellular plants and fungi reproduce asexually as well.Binary fissionIn binary fission the parent organism divides in two daughter organisms, Manysingle-celled organisms, both prokaryotes (the archaea and the bacteria), andeukaryotes (such as protists and unicellular fungi), reproduce asexually throughbinary fission; most of these are also capable of sexual reproduction.BuddingSome cells reproduce by budding (for example baker's yeast), resulting in a 'mother'and 'daughter' cell. The offspring organism is smaller than the parent. Budding isalso known at a multicellular level; an animal example is the hydra, whichreproduces by producing buds . The buds grow into fully matured individualswhich eventually break away from the parent organism.Vegetative reproductionVegetative reproduction is a type of asexual reproduction found in plants wherenew individuals are formed without the production of seeds or involvement of146

gametesby meiosis or syngamy. Examples of vegetative reproduction include theformation of plantlets on specialized leaves (for example in Bryophyllum and someproduce new plants out of rhizomes(Ginger) or stolon (for exampleSpider plant).Other plants reproduce by forming bulbs or tubers (for example bulbs of onion andpotato tubers). Some plants produce adventitious shoots and suckers(Chrysanthemum) that form along their lateral roots.Spore formationMany multicellular organisms form spores during their life cycle calledsporogenesis. Exceptions are animals and some protists, who undergo gametic meiosisimmediately afterfertilization. Plants and many algae on the other hand undergosporic meiosis where meiosis leads to the formation of haploid spores and not thegametes. These spores grow into multicellular haploid individuals (calledgametophytes in the case of plants) without a fertilization event. These haploidindividuals give rise to gametes(haploid) through mitosis. Meiosis and gameteformation therefore occur in separate generations or "phases" of the life cycle,referred to as alternation of generations.Fungi and some algae involve mitosis giving rise to reproductive cells calledmitospores that develop into a new organism after dispersal and germination undersuitable conditions. This method of reproduction is found in conidial fungi and thered alga and involves sporogenesis without meiosis. Thus the chromosome numberof the spore cell is the same as that of the parent producing the spores. However,mitotic sporogenesis is an exception and most sporesof of Basidiomycota, and manyalgae, are produced by meiosis.FragmentationFragmentation is a form of asexual reproduction where a new organism grows froma fragment of the parent body. Each fragment develops into a mature, fully grownindividual. Fragmentation is seen in many organisms such as animals (some147

oundworms and sea stars), fungi, and plants. Some plants have specializedstructures for reproduction byfragmentation, such as gemmae in liverworts. Mostlichens, which are a symbiotic union of a fungus and photosynthetic algae ,reproduce through fragmentation to ensure that new individuals contain bothsymbionts.Student Activity-3.1Material required: ICT facility, textbooks for photographs and diagrams oforganisms that reproduce asexually,Procedure:1. A day before lesson begins ,students may be asked to search the Internet andtextbooks for photographs and diagrams of organisms that reproduceasexually, including fission, vegetative propagation, budding, fragmentation.2. Give the workseet:3.1and 3.2,3.33. Ask students to discuss worksheets and students to share their examples.Challenge the students to come up with the correct definitions and examplesof organisms that participate in different types of asexual reproduction. Directstudents to make notes on the basic types of asexual reproduction.4. Tell students that they will get to observe asexual reproduction in theclassroom. ExlainActivity-3.2, Asexual Reproduction( Laboratoryexperiments) for two examples that students can do, or that you candemonstrate to the class. These exxperimentsdemonstrate only fission andvegetative propagation, since they are the easiest to demonstrate in aclassroom setting. You may choose any or both of the experiments for yourclassroom, as time permits. Activitiesmay also be split among student groups.5. As laboratory activities are completed, have students to note theirobservations. The students should attempt to answer the questions that are148

given with each activities. These questions can be discussed with the class asthe lab activities are conducted or after all lab activities are done.Technology Connections:Students may be advised to access Web sites for the United States Department ofAgriculture at http://www.usda.gov and the National Biological InventoryInitiative at http://www.nbii.gov, and search for the term "asexual reproduction".Worksheet-3.11. Identify three ways how you could duplicat any picture given to you .A.B.C.2. Match the following types of asexual reproduction with appropriateexamples given in series 2- 9A. fissionB. fragmentationC. buddingD.E. vegetative propagation_________1. Cell division results informationof a bud and as it grows, forming anidentical copy of its parent, then separating from the parent to become independent._________2. Paramecium or protists_________3. Single-celled organisms that reproduce by splitting in two.149

_________4. Spider plant and geraniums_________5. Growing a new plant without a seed._________6. Hydra_________7. An animal that grows from a separated piece of a parent animal.8. On the reverse side of this paper, describe the five types of asexualreproduction; fission, fragmentation, budding, parthenogenesis, vegetativepropagation. Name one organism for each kind of asexual reproduction.Student Activity : 3.2Asexual Reproduction- Laboratory ExperimentsThese laboratory experiments will demonstrate vegetative propagationExperiment : 1 Vegetative PropagationProcedure:1. Cut a baby plantlet, with 6 cm of stem attached, from a spider plant.2. Carefully place stem of the detached plantlet into a cup of water.3. Place on a well-lit shelf, in a room with proper ventilation.4. Label and note date.5. Check daily for any signs of mould (changes in smell, water color, decay ofplant). If signs of mould are present, discard the plant and once again startthe procedure.6. Completely change the plant‘s water weekly.7. Record findings.150

8. Plant it in the soil when roots have formed.Answer the QuestionsWill the spider plant sprout roots and develop into a new plant?How is asexual reproduction be beneficial to these plants?Experiment II- BuddingProcedure:1. Place a 2 ml of yeast grains and a 1 ml of sugar in a Petridish.2. Add 4 ml warm water,cover and keep it in a warm place for 10 minutes. (Yeastmultiply fastest at 24 0 to 27 0 C.)3. Smear a yeast sample on a slide plate with a sterile toothpick.4. Cover it with the cover slip carefully.5. Look under a 40x microscope6. Record drawings of the yeast budding and label it.7. Discard yeast properly.151

Worksheet-3.2• Using a Venn diagram, compare and contrast any three of the five types ofasexual reproduction at one time. Try different combinations to understandwhat do all five types of asexual reproductions have in common. Put sharedcharacteristics where the circles overlap and write different characteristics in theparts of the circles that do not overlap.1. fission2. vegetative propagation3. budding4. fragmentationDescribe what do all five types of asexual reproduction have in common.Worksheet-3.3Students may be guided too visit a greenhouse, or botanical garden in the spring to view propagation ofplants by cuttings.o Identify plants in their homes which reproduce by asexual reproduction. After collecting first hand information ,let students draw and label the diagrams .ims.ode.state.oh.us/ODE/IMS/Lessons/Content/CSC_LP_S02_BB_L06_I05_01.doc · DOC file152

Activity-4Vegetative Reproduction in plants-Vegetative propagationLearning OutcomesAfter completing this lesson, the students will be able to:Define vegetative reproduction (or propagation) in plantsList the specific plant structures which participate in vegetative propagationand describe their general, morphological features with examples.(refer tocontent of activity-3)Name and draw roots, stems and leaves, etc, specialized for vegetativepropagation.Relate between natural and artificial ways of vegetative propagation.Differentiate between cuttings, layering, gootee and grafting by givingexamples.Define micro propagation and describe methods employed in it.State advantages of micro propagation.Describe the advantages of vegetative propagation.Material RequiredRunner stemsSuckersBulbsRhizomesBryophyllum leaves having developing buds.Charts showing one or all the vegetative reproductive structures.Video showing the procedure for grafting, layering, or buddingAnimated video or story about the process of vegetative reproduction namelylayering,.153

Charts showing the process of artificial propagation using marcotting, layering,cuttings, budding, grafting.Resource person/Trained Gardener to talk to learners about artificialvegetative reproductive means.Content:Vegetative Reproduction is the production of new plants from any vegetative part ofthe plant except seed. Most Angiosperms reproduce sexually with the help of theirflowers and produce seeds. But some plants reproduce by other structures(vegetative parts) like root, shootor leaves, In this lesson we will study about variousways of vegetative reproduction by different parts of the plants.A common experience : Most plants which reproduce vegetatively in natureusually have small daughter plants growing around them. You may easilynotice this phenomenon in many plants in your vicinity, e.g. banana, cannas,ferns,ginger.These plants have aerial portions with green leaves and they also have athickened modified stem (rhizome) growing horizontally under the soil. Fromthe axillary bud of this underground stem new young plants grow out likethe "babies of the mother plant". Over the passage of time, these young plantsdevelop their own root system. When separated from mother plant they growindependently. This is an example of Natural vegetative Propagation.Vegetative parts which is involved in reproduction have primary or secondarymeristems, capable of active cell division, and thus can give rise to new plants.NATURAL AND ARTIFICIAL MEANS OF VEGETATIVE PROPAGATION.Many small plants which you see growing vegetatively near the mother plantare propagating naturally.154

Man has taken advantage of this natural phenomenon and has artificiallypropagated plants vegetatively by using the specialized vegetative organs bycuttings, grafting and layering.When we use the vegetative parts for propagating crops or ornamental plants,it is termed artificial vegetative propagation.Student Activity : 4.1Vegetative PropagationMaterial required a potato with many eyes (dormant shoot buds), toothpicks,plastic container, water., room with proper ventilation.Procedure:1. Select a medium size potato with many eyes (dormant shoot buds).2. Slice the potato in half.3. Using toothpicks suspend half the potato in a clear plastic container with thefresh cut side of the potato facing the bottom of the container. Make sure thatmost, not all, of the potato is submerged in water.4. Fill the jar with tap water.5. Label and date the jar.6. Place the jar on a well lit shelf, in room with proper ventilation.7. Check daily for any signs of mold (changes in smell, water color, decay ofplant). If signs of mold are present, discard the plant.8. Do not let water go below about half the potato, and completely change theplant‘s water weekly.9. Record the findings every day.155

Worksheet-4.1Answer the questionsQ.1 Are all potatoes capable of reproduction?Q. 2 Which part of potato is responsible for reproduction?Q.3.Which kind of reproduction takes place in potato? Why do you say so??Q.4 . Can potato reproduce by sexual mode?156

Student Activity : 4.2Procedure : Teacher may collect following Fresh or preserved specimens/charts /videos and explain vegetative reproduction in plants with these aids,Slide of yeast showing buddingSlide of Spirogyra showing FragmentationTuberous roots of sweet potatoFasciculated roots of DahaliaRunner of wood-sorrelSuckers of ChrysanthemumRhizome of gingerTuber of potatoBulb of OnionCorm of AmorphohallusAdventitious buds of BryophyllumVEGETATIVE REPRODUCTION IN LOWER PLANTS(i)Binary fission:. The simplest kind of vegetative reproduction is seen in uni-cellular organisms such as bacteria, yeast andamoeba. In these organisms, thecell divides into two and each grows into an adult cell after separation.(ii) Fragmentation: In certain filamentous algae like spirogyra if the filament getsbroken accidently into two or more portions, each portion is capable ofgrowing into an independent individual by mitotic cell divisions.157

VEGETATIVE REPRODUCTION IN HIGHER PLANTSBy various plant partsVegetative reproduction can occur from any part of root, stem or leaf. Vegetative reproduction by roots :You are familiar with various modifications of roots such as for storage of food,for support, etc. Some of the roots also help in vegetative propagation.Tuberous roots or fasciculated roots of sweet potato asparagus and of Dahliawhen get detached from the parent plant can grow into a new plant. Theseswollen roots have abundant stores of reserve food which is used during activegrowth at the time of sowing. Such roots can also be called roots stocks becausethey can be stocked for sowing in the next season.Tuberous roots of sweet potatoFasciculated roots of DahliaVegetative reproduction by stem :Vegetative propagation by various kinds of stem is quite common. A fewexamples of such stems are as followso Runners158

They are seenin common lawn grass (Fig. 34.3). These are horizontal stems runninghorizontally parallel to the ground. The inter- nodes are long. New roots develop atthe nodes. The axillary buds at the nodes grow upward to form new shoots, thusforming a sort of new plant.o SuckersRunner of wood-sorrelSuckers of mint and Chrysanthemum are somewhat similar to runners but withshorter internodesSuckers of Chrysanthemumo RhizomesRhizomes are underground stems of ginger, canna and banana. These areirregularly in shape and grow horizontally and are adapted to store food.. Theyhave nodes and internodes. Thin dry brownish papery scale leaves are presenton the nodes. Axillary buds are also present on the nodes. When the conditionsare favourable the underground buds grow into aerial shoots. to form newplants.159

Rhizome of gingero Tuber,Example : potato Tuber, it develops by the swelling of the tip of lowerunderground branch which gets and is adapted for food storage. A tuber hasbuds, popularly called eyes" in the axils of scars of scale leaves ("eye-brows"). Thetwo together represent the nodes of an ordinary stem.,, The potato tuber alsocontains an apical (terminal) bud. Every piece containing a bud is potentially,capable of pro- ducing a new plant.Tuber of potatoo CormCorm is a condensed form of rhizome which is formed vertically in the ground.Sometimes a single corm may also develop secondary or daughter corms as incolocasia, gladiolus, Amorpho phallus160

-Corm of Amorphohalluso BulbsBulbs are found in onion, lily, tulip, etc. A bulb is a thick, short, undergroundstem in the form of a disc, which bears overlapping scale leaves containing food.The terminal bud grows into a green aerial shoot under suitable conditions.Bulb of OnionVegetative repoduction by Adventitious buds on leaf.Leaves of a number of plants produce adventitious buds in their marginalnotches (Bryophyllum). These buds usually remain dormant in intact plants.When leaves are detached or touch the soil with proper moisture, dormancy ofthe buds ends and each notch is able to produce a small new plant. Vegetativepropagation by fleshy leaves of different kinds of rose cactus (kind of succulents)161

are also very common. When leaves get deta- ched from the main plant andmoisture is available the leaf base produces a new plant.Adventitious buds of BryophyllumVegetative reproduction by BulbilsIn plants such as certain varieties of pineapple, some of the upper and lowerflowers of the inflorescence instead of developing in to fruit and seeds becomemodified into small tufts called bulbils. These fall on the ground and grow intonew plants.ARTIFICIAL MEANS OF VEGETATIVE PROPAGATION(a) Utilization of specialized vegetative structures : Some specialized structures as tuber, corm, rhizome, bulb, runner andsucker which produce new plants naturally have been described andillustrated-above. Man has used these structures for artificial'multiplication of such plants in agriculture and horticulture in order tog.et larger number of plants in short duration for his personal benefit.(b) Cuttings -Cuttings refer to regeneration of pieces of roots, shoots etc. andformation of a complete plant from them Many plants like rose, bougainvillea, croton, coleus money plant, ,sugarcane are grown through cuttings from their stem. Stem cuttings of162

some of the plants can be grown even in water, where they strike rootsand develop adventi tious buds.(c)Layering In this method a lower branch of a plant is bent down and covered withmoist soil, leaving the growing tip above the soil. A ring of bark isremoved from the stem before it is bent down. In a few weeks time whenenough roots have developed on the underground portion above theringed part, it is clipped off from the parent plant and grown separately asan independent plant. This is a common practice with plants like jasmine,straw-berry, grapewine, bougainvillea.LayeringAerial-layering or gootee is a similar practice where bending of branchesis not possible because of the height of plant or due to woody nature ofstem. In this method a ring of the bark is removed from a selected branchat a specific sight, and it is covered with moist moss and enclosed in apolythene sheet. When roots appear, the stem is cut below the roots andplanted to form a new plant163

Gootee(d) Grafting : Grafting is an ancient and very useful horticultural practice. This consistsof inserting a small branch into a rooted plant. The rooted plant taken as astock is resistant to diseases and is physically sturdy. In this stock a branchis inserted which is known as the scion or graft. The scion or graft is thestem cutting from the desired plant of the same species. Usually thegrafting ends of stock and scion fit well with each-other and are boundfirmly with tape or rubber band, until their tissues unite and vascularcontinuity is established Grafting is mostly practised in dicotylodon Plantsand not possible in monocotyledon plants.. Grafting has been foundextremely useful in propagating improved varieties of various flowers andfruits like rose, bougainvillea, lemon, orange, mango and apple. It isespecially important for propagation of seedless varieties of plants in ashorter duration.164

B. Artificial means of Propagation in Laboratory-THE MICROPRO PAGATION /TISSUE CULTUREIn this method, the technique of culturing plant cell, tissue or an organ isutilized for propagation of plants.A small piece of tissue, organ or even a single cell is taken from a plantand is transferred to a sterilized container with proper nutrient medium inan aseptic conditions The tissue grows quite fast into an unorganizedmass, called callus. The callus can be maintained and multiplied for anunlimited period. When small portions of the tissue are transferred toanother specialized medium with appropriate hormones( responsible fordevelopment of root or shoot) , it induces differentiation and plantlets(little plants) are formed.Embryoid formation on tissue cultures of better up.165

A- An unorganized callus; (=the embryoid have developed into plantlets, and afresh crop of embryoid is seen arising from the surface of the hypocotyledonregion of these plants;B- the embryoid bearing portionC and D- enlarged form.• The plantlets can be transplanted in a pot or soil by a gradual procedure andbe grown to mature plants.Importance of MicropropagationBy this method an indefinite number of identical plants can be obtained vegetativelystarting from a small amount of parent tissue. In orchids, carnations,chrysanthemums and asparagus micropropagation has been used very successfully.Recently large scale planting of cardamum plants by micropropagation is beingsuccessfully tried in some part of our country.http://www.lessonsnips.com/Worksheet - 4.21. Give one example and draw a labelled the diagram for each of the followingmodes of propagation, bya) Rootsb) runner166

c) suckerd) tubere) cormf) bulbg) leaves167

Worksheet- 4.3Answer the following1. Define vegetative reproduction2. List plant parts used in vegetative reproduction3. Explain vegetative reproduction using leaves of Bryophyllum4. Describe structure of stem tuber and bulb168

5. Draw and label parts of sucker and rhizome6. Describe parts of a corm7. List differences between a rhizome and a corm8. Draw and label vegetative reproductive organs9. Explain how stem cuttings are used to produce new plants10. Describe the procedure used in layering, grafting, to produce new plants169

11. Explain the importance of artificial propagation with regard to cropproduction and profitability12. Does Rose reproduce by seeds? Ask your Gardner and discuss in the class.Source:www.Lessonstrips.com170

Activity : 5Asexual and Sexual ReproductionLearning Outcome:Understand the significance of Asexual and Sexual Reproduction operating innature.Compare and contrast two types of reproduction found in natureContent:We have already studied the importance of reproduction in life of organisms and, inthe context of evolution,they must choose the one most suitable from amongdifferent methods of reproduction. There are two major strategies forreproduction—sexual and asexual. Each process has its own advantages anddisadvantages, and each is appropriate for survival of the organism in certainsituations. Vertebrates, such as humans, are almost exclusively sexual in theirreproduction, many simpler animals are asexual. To decide which reproductivestrategy may prove to be advantageous in a given set of circumstances, it isimportant to understand how they differ.Asexual ReproductionAsexual reproduction may be found invariety of forms. The simplest one-celledorganisms may reproduce by binary fission, in which the cells simply divide in half.This form of reproduction creates a clone of the parent, and has the advantageofusually being very quick and energy efficient. For example, bacteria that reproduceby binary fission can give rise to progeny every few hours.In multicellular organisms, a similar practice called fragmentation isobserved. In this process, small pieces break off and grow into neworganisms. Still other organisms reproduce by budding, in which a smaller171

copy of the parent grows on the body because of cell division and eventuallysplits off from parents to begin life on its own.All these variations of asexual reproduction have one thing in common,the offspring is a direct clone of the parent. The purpose of reproduction isto propagate one's own genes. Asexual reproduction is a good deal for theparent. It is quick, simple, and the genes of the parent will not be dilutedby those of another individual. In addition, an organism that reproducesasexually can reproduce about twice as fast as one that reproducessexually.Sexual ReproductionSexual reproduction is much more complex than asexual reproduction. Itrequires the production of sex cells, or gametes, which have half thenumber of chromosomes of all other somatic (body) cells in the organism.When in the body of the organism there is a time/need to make sex cells,it undergoes meiosis, resultingin haploid cells (one copy of the genome)from diploid cells (two copies of the genome). A key advantage of meiosisis that the two copies (2sets) of a single chromosome can cross over tocreate a completely new chromosome that contains a new combination ofgenes. The net effect of crossing-over is that genes on a specificchromosome can change position from one chromosome to the next(homologous chromosome received from two parets). This means thatgenes from both parents may end up next to each other on the samechromosome. Once the gametes are made in the male and female, theymust meet with one another to form offspring i.e. fertilisation. The spermfrom the male provides one copy of a genome. The egg from the femaleprovides another copy of a different genome. Thus, the offspring ofsexually reproducing organisms receives genes that have more than oneopportunity to switch genes around or form new combinations —firstduring crossing-over and second the random union of the twogametes.172

Comparing Sexual and Asexual ReproductionHowever, note how much energy sexual reproduction utilises. The sexcells must be made, and as each parent contributes only half the genome,it propagates only half as many genes toeach offspring as does anasexually reproducing organism. Recall that in nature an organism is mostinterested in propagating its genes; indeed, that is the whole point ofreproduction. To reproduce sexually is to contribute the reduced amountof genetic material that one reproduces i.e. by half, and this reduction doesnot even take into account the effort sexually reproducing organisms needto make to find mates, then impress, select, or defend them. Nevertheless,nearly all higher animals reproduce sexually. Why? The most importantaspect of sexual reproduction is the opportunity it provides to successfulgenes to switch around. If it is beneficial to an organism's survival to beboth tall and have blue eyes, a short, blue-eyed parent and a tall, browneyed parent can together stand a good chance of producing off-springwith both favourable characteristics. If they reproduced asexually, a short,blue-eyed parent / tall, brown eyed parent would have to wait aroundfor a height/eye colour -inducing genetic mutation to change height andeye color. And because mutations, rate in most organisms is exceedinglyslow, it might take an asexually-reproducing parent hundreds orthousands of generationswhile it would take only a generation forsexually-reproducing parents to beget tall offspring with blue eyes!Asexually reproducing organisms do not readily share genetic material,but they do reproduce much faster. And because asexually reproducingorganisms reproduce faster, they do exceptionally well in situations wherethey is no change in environmental conditions and have no competition.With sexually-reproducing competition nearby, however, the asexualorganisms may quickly be outadapted and outevolved by their neighborsi.e. sexually-reproducing organisms, even though the asexual organisms173

may have superior numbers due to fast reproduction. Many biologiststhink that intense competition gives rise to sexual reproduction, becausethe competition requires rapid innovation and distribution of the mostsuccessful genes.for successful survival as environental conditions keepchangingDoes it mean that sexualreproduction, with all its demands, is worth themoderate amount of recombination that results fromit? If not, why do allvertebrates, many invertebrates, and most plants sexually reproduce? Itseems likely that the ability to swap around already considered to besuccessful genes, rather than being forced to wait for mutations which is amatter of chance, is a more successful strategy for complex organisms.And less complex organisms can survive by without investment of thelarger energy and resource that sexual reproduction demands.http://www.bookrags.com/research/reproduction-asexual-and-sexual-ansc-04/174

Student Activity : 5.1Using the two minute talk as an warming upstrategy, students will discuss priorknowledge and focus on differences between asexual and sexual mode ofreproduction.The students will learn that in asexual reproduction the sole parent is involved andpasses copies of all its genes on to its offspring.Also, they will recallthat sexual reproduction usually results in greatervariationsince two parents give rise to offspring that have unique combinations ofgenes inherited from two parents.The students will discuss with each other and tell what they know about asexualand sexual reproduction.Procedure:1. Let the students group in pairs.2. The students will give a talk of two minutes on what they know aboutasexual or sexual reproduction.3. They may choose who will speak on which topic i.e. sexual or asexual andwho goes first by finding out whose birthday comes first / which ever is theolder will go first. Then the other student will go.4. Use a stop watch to signal the first students to begin his/her talk.5. After two minutes remind the student to wind up by sound of a bell. Thenthe other partner will begin to talk.6. Repeat this with few groups and7. Finally, let a few students to summarise their responses with the entire classwhen the activity is done with the help of Learning Frames ( Given below).175

Student Activity: 5.2Learning Frames (refer to teacher’s note)Procedures:In this summarizing activity, students may be asked to focus on what they learnedabout asexual and sexual reproduction.1. Display a transparency of the Learning Frame. Explain to the students thatthey need to fill in information on what they learned about asexual andsexual reproduction.2. Prepare the learning frame by using information that you learned in thelesson.3. Read the frame aloud turn by turn.4. Then, pass out a blank learning frame to each student.5. Allow students to fill out their learning frame withwhat they learned aboutasexual and sexual reproduction.Worksheet-5.1Answer the following questionsQ.1 Why in nature asexual reproduction still continues to exist?Q.2 Write two advantages and two disadvantages of asexual reproduction.Q.3.What is the significance of sexual reproduction over asexual reproduction.?176

Worksheet-5.2Procedure:Using the Venn Diagram, students will be able to compare and contrast concepts onasexual and sexual reproduction.1. The students may use the internet or the content of the chapter to help themlook up information on asexual and sexual reproduction.2. The students will use Microsoft Word to show how asexual and sexualreproduction comparision.3. Students have to draw two partially overlapping circles on Microsoft Wordusing drawing tools.4. They will label each non overlapping side using a text box, one side AsexualReproduction and the other side Sexual Reproduction.5. Tell the students to fill in the asexual reproduction side with attributesbelonging to it.6. Then fill in the other side, sexual reproduction with its attributes as well.7. Finally, have them fill in the overlapping area with what bothhave incommon.177

Activity-6Importance of sexual reproductionLearning Outcome:Understand the need of sexual reproductionLearn that variations, which arise during sexual reproduction, are importantbecause they allow survival of species and they lead to evolution.Comprehend that Variations in nature are random. Both positive andnegative variations may occur. However, only positive or beneficialvariations are retained. The negative variant is gradually lost from the genepool.ContentThis is a fairly a simple concept to understand. Evolution depends on changes ingenetic makeup of a species over time. Sexual reproduction allows for geneticchanges to occur in each successive generation. This is because sexual reproductionoccurs using only half the genetic information from the male and half from thefemale. As such this helps to increase the variability of the offspring which either donot allow offspring to survive or will help the offspring to live a successful stronglife and eventually passing its genes onto the next generation. The reason being thatnature only selects those which are best suited to live in an environment which isdynamic, and these are likely to survive (natural selection). As they are likely tosurvive they also pass on genes to the next generation meaning that as long as theconditions in the environment are stable the next generation will be even bettersuited to survive in that area. Without this variability a slight change in theenvironment conditions could result in the extinction of that particular speciesbecause they cannot adapt. In asexual reproduction, living organisms pass on acomplete set of their own genes to their offspring .This type of reproduction isdangerous in case a disease came along, that was lethal to animal X, who has no178

esistance to the disease but it reproduces by asexual mode only. In the absence ofresistance gene there is no possible way in which its offspring could inherit characterof resistance (except for mutation which is rare and a matter of chance) and have achance to survive. This may become a reason for its genetic legacy to be lost.Student Activity- 6.1In the following activity, each child will demonstrate crossing over by making a claymodel of chromosome (refer to teacher note0Materials: Red and blue plasticeneProcedure:1. Make one chromosome using red plasticene. Each chromosome is made oftwo identical Strands (chromatids) held together by the centromere. Thecentromere can be shown as a ball of red plasticene.2. Make another chromosome using blue plasticene having the same size andshape (homologous chromosome).3. Show how different crossing over can occur. Show how double crossoversoccur.4. Slowly separate the two chromosome with exchanged parts (Two colours inone chromosome).Answer the followingHow does crossing over explain genetic variability?http://www.glencoe.com/sec/science/voyages/voyagesgreen/unit6/chapter16/svna7n16-2.pdfChapter 16http://www.glencoe.com/sec/science/voyages/voyagesgreen/unit6/chapter16/svna7n16-2.pdf179

Student Activity - 6.2Role Play: Students will perform an act to depict Meiosis where chromosomes pair,exchange DNA material, segregate, reorganise and replicate in daughter cells.Chromosomes in daughter cells are not identical as parent cells but combination oftwo parent cells and give different characteristics to daughter cells resulting invariation.Material required:ChalkDusterCut outs with un labeled diagrams showing the stages of meiosisChart showing stage of MeiosisCD-ROM or videos showing stage of MeiosisRed and blue coloured kite papersRecord sheetProcedure:Teacher may Show CD-ROM, videos or Chart showing stage of Meiosis to students.Give following instructionsAn out line of the cell may be drawn with the help of a chalk on the floor..Nuclear membrane /Cell membrane may be drawn or removed with thehelp of a chalk and a duster respectively (as and when required).This particular cell has 6 chromosomes. Each student represents a chromosome and pair of hands of a studentrepresent a pair of chromatids of a chromosome. Two students representinga pair of homologous chromosomes180

Students will use manipulative such as red or blue colour kite paper on thesleeves.All the three chromosome representing one set of chromosome (Inheritedfrom mother) will use red colour kite paper on sleeves and all the threechromosomes of another set(inherited from father) will use blue colour ofkitepaper on the sleevesEnact the movement of chromosomes in different the stages of meiosis oneby one.To demonstrate the changes in DNA while cells undergo meiosis (crossingover),students may be guided by the teacher to exchange part of thecoloured kite paper on their sleeves.Later students can do a self- or peer- assessment for the activity they havejust performed to assess how well their skit reflected the events of meiosisshown in the video. .Students will complete their recording sheet to outline the major changes inthe DNA during meiosis.181

Worksheet-6Label the following diagrams of the stages of meiosis.1. _________________________ 2. _________________________Figure 13. _________________________ 4. ___________________________182

Answer the following questions.5. In what way is meiosis II similar to mitosis?______________________________________________________________________6. How are gametes different from other (somatic) cells in the body?______________________________________________________________________7. What happens during fertilization?______________________________________________________________________8. What is the total number of paired chromosomes in a body cell called?______________________________________________________________________9. Do centromeres divide at anaphase I or II?______________________________________________________________________10. Starting with one cell, how many haploid sperm cells are formed at the end ofmeiosis?______________________________________________________________________183

Activity-7The Structure and Functions of FlowersLearning Outcome:Identify the structure and function of various parts of the flowerContent: The Structure and Functions of a FlowerPETALS, COROLLA, SEPALS, CALYXFlower is the reproductive structures in higher plants. Male amd female reproductiveorgans are contained within flowers. Flowers have more than one petal, and the flowerpetals are collectively called the corolla. A flower when in bud condition ,isprotected by green leafy structures called sepals. Collectively, all of the sepals formthe calyx.The corolla or petals are often brightly coloured to attract insectsor birds. The flowersmay also be scented. For instance, Honeysuckle has showy, attractive flowers whichattract insects by day. However, in the dark, their colourful showmay not he, and theirheady scent then helps to attract night-flying moths.184

In insect-pollinated plants, there are also usually nectaries which secrete sugary nectar,located and are located within the flower. These provide an incentive to insects to visitthe flowers. In the search for nectar, the insects will often get pollen grains caught ontheir bodies from anthers which are held up on filament..The insects may then brush offonto the stigma of the next flower they visit and in this way the flowers get pollinated.The receptacle is the place on the stem where floral organs originate and attach.The Female Reproductive Organ: The CarpelThe female parts of a flower known as carpel consist of an ovary, which extends atubular structure called the style and on the top of the style is a surface receptive topollen called the stigma. ,The stigma can be of many different forms, most of them designed to help trap pollenfrom various agency like wind,water or animals. There are many variations on thisbasic structural theme.The ovary is at the base of the carpel. It contains one or more ovules in it.Style helps to connect stigma with ovary and is used as passage for male gametesreceived at stigma to reach ovules present in ovary.After fertilization the ovule becomes the seed and the ovary becomes the fruit.The Male Reproductive Organ: The StamenThe male parts of a flower consist of one or more stamens. Each stamen is made up ofpaired anthers (sacs containing pollen) on a filament or stalk.185

The anthers are the orange/yellow structures often seen in the centre of a flower. Thecolour of the anther is because of the presence of large quantity of pollen grains whichare formed in anthers.Pollen from the anthers of one flower is transferred to the stigma of another usuallyeither by wind, water or by animals, especially insects.Pollen from a flower after landing on stigma of another flower, may develop a pollentube on stigma in order to help reach male gametes to the female gamete ,only when itfalls on the same species flower.http://leavingbio.net/TheStructureandFunctionsofFlowers%5B1%5D.htmStudent Activity : 7.1Audio-visual activity-http://www.powershow.com/view/19f6d-Mzc3M/Flower_Dissection_ActivityWorksheet-7AParts of a FlowerWord List: petal sepal stamen another stigma ovary pistilProcedure1. Observe your flower specimen. Use a magnifying glass to see greater details offlower part structures. Write three detailed descriptive sentences of your particularflower.186

a) _____________________________________________________________________b) _____________________________________________________________________c) _____________________________________________________________________Dissect the flower and draw the Diagrams in the boxes given, also give answers toquestions given below:PetaldiagramPetals and SepalsHow many colored petals are present?______________________________________________________________________________________________________a) What advantage do the flowers get by having coloredpetals?______________________________________________________________________________________________________b) How many green leaves like structures surround the bottom of the flower?__________________________________________________________________________________________________________________________________________c) What is their function?__________________________________________________________________________________________________________________________________________Stamen and AntherRemove enough petals from the flower so that you can observe the inner parts. Do yousee a large stalk like structure in the center of the flower? This part is called the pistil.Surrounding the pistil are several upright stalks.187

Questions:a) What are these called?______________________________________________________________b) If you observe carefully, you can see structures attached to the top of the stacks.What are these called?______________________________________________________________c) do they produce?______________________________________________________________Stamen and anther diagram188

1) Examine the anther with a hand lens.2) Add a drop of sugar solution to a microscope slide. (The sugar solution is to imitatethe sugary surface of the stigma.) The pollen tub uses the sugar to produce energyfor growth.3) Place a yellow anther on the drop of solution and stir it around with a stirring rod.4) Remove the anther and add a cover slip over the drop of solution.5) Examine the pollen under a microscope.6) Draw a diagram do what you see.Pollen grains diagram2. The diagram given below is a typical flower. Your flower may be slightly different,but will have the same types of flower parts.A) Using your forceps, carefully take the flower apart and set them on a sheet ofpaper napkin.B) Use the diagram to identify each part.C) Draw your own diagram of each part in the spaces . Provided on yourworksheet . Use your magnifying glass or dissecting microscope to see anddraw greater detail.189

D) Label your drawing and answer the questions.Stigma, Pistil and Ovary1) Draw and label a diagram of the stigma, pistil, and ovary.2) Use the razor blade to cut open the ovary of the flower All the odd roll numbersof the class will do a cross-sectional cut. The even numbers will do alongitudinal cut.Stigma, pistil, and ovary diagram3. Draw a diagram of what you see.If the ovary is mature,you may observe a number of chambers inside it in its crosssection. These chambers contain the seeds that are in their formative stage. Labelyour diagram to show the chambers and the seeds .190

Ovary sectionQuestionsa) Is the ovary divided into parts? If so, how many?________________________________________________________________________b) When the ovary matures, forming a fruit, how do you think it will look?________________________________________________________________________Worksheet-7B1. Answer the following questions. Write main one function of each of thefollowing flower parts.Stamen:Anther:Filament:Pistil:Stigma:Ovary:191

Pollen tube:Petals:Sepals:Activity-8Sexual Reproduction in plants-IIPollination and FertilizationLearning Outcome:Understand the structures of (Pollen and Embryo sac) involved in the process ofreproduction in plants.discuss the process of pollination and fertilization in plantsContent:The sex cells of the flowering plant are called gametes. There are both male and femalegametes thus the flower undergoes sexual reproduction.Male GametePollen Formation: Pollen Grains develop within the Pollen Sac of an anther:192

Each pollen grain is surrounded by a thick, tough protective wall called an exine. Thisis a tough covering that allows the pollen grain to survive harsh conditions for longperiods of time after it is taken away from parent plant. The intine is another thinprotective coating in side exine.The nucleus of pollen grain divides by mitosis to become two nuclei. One is the tubenucleus which supports growth of the pollen tube. The other is a generative nucleuswhich later divides mitotically to form two male gametes.As the anther ripens, the pollen sacs burst open and the mature pollen grains are readyfor dispersal.Development of the Embryo SacEach ovary contains one or more ovules. The green structure at the bottom of the carpelis the ovule. The integuments are the 2 walls of the ovule. There is a small opening inthe walls called a micropyle. From here the pollen tube enter s carrying male gametes tohelp reach egg cell in ovule.The embryo sac, also known as the megaspore, divides by meiosis to form 4 haploidcells. Three of these cells degenerate and one remains. Only one megaspore survives ineach ovule. This becomes the embryo sac. The haploid nucleus of the survivingmegaspore undergoes three mitotic divisions. Eight haploid nuclei are now present.193

Within the swollen ‗megaspore cell‘ six haploid cells and two ‗polar nuclei‘ are formed.The entire structure is called the embryo sac. One of the cells near to the micropyle endof the ovule behaves as the haploid female gamete (egg cell).The Carpel With a Mature Embryo Sac as shown below:PollinationPollination is the transfer of pollen (male gamete) from the anther to a stigma.Cross-pollination: pollen is transferred to the stigma of flower of another plant.Self-pollination: pollen transferred to the stigma of the same flower or a flower of thesame plant. Ensures reproduction in absence or inefficient pollinating agent.Pollination can be accomplished by the wind, water or by animals. Insects are the mostcommon animals that will pollinate a carpel.The most common relationships between plants and insects are generally thoseinvolving bees. Bees collect pollen and nectar as food for themselves and also to feedtheir young. For this reason bees have developed a number of adaptations that makethem particularly good pollen carriers. Bees have special hairs that are arranged to formpollen 'baskets' towards their hind legs and the underside of their abdomen. These194

adaptations allow them to gather and carry large volumes of pollen and nectar. Bees areideal pollinating agents because they visit many flowers and carry lots of pollen,before returning to their honeycomb in their nests. So the chance that a bee will transferthe pollen between flowers of the same species is very high.Many insects eat pollen. In the process of eating they become covered by it. Pollinationhappens when the pollen feeder i.e. insects transfer the pollen to the stigma of the sameflower or another flower of the same plant, or flower on the another plant of the samespecies, as the insect looks for more pollen to eat.Fertilization: An ovule in the ovary of a pistil , contains an egg cell ( and a diploidfusion nucleus, which is created through the joining of two polar nuclei within theovule). When a pollen grain belonging to the same species comes into contact with thestigma, it grows to form a pollen tube through style , down into the ovary at the pistil'sbase. As the pollen tube penetrates the ovule, it releases two sperm (male gametes) cells.One fuses with the egg to create a diploid zygote, (while the other joins with the fusionnucleus to form a triploid nucleus. This triploid nucleus turns into an endosperm,which nourishes the developing embryo, filling the role of gametophyte tissue in theseed), and later the ovule becomes a seed,http://leavingbio.net/TheStructureandFunctionsofFlowers%5B1%5D.htm195

Student Activity:Audio-Video Activityhttp://www.youtube.com/watch?v=X7uH46X0G5YAnswer the following2 Define pollination?Worksheet-8A3 How do pollens travel from anthers to the stigma of same or another flower?4 Why are ferns and mosses uncommon on most school grounds?5 Mention one characteristic of plants adapted for wind pollination, InsectPollination and Bird pollination(a) Explain how each of these characteristics assists pollinating agents.6 Explain why cross-pollination is better for a plant species than self-ollination.7 Why is it necessary for pines to produce large amount of pollens?196

Worksheet-8B1 Which of the following is the correct sequence for the pollen tube to eventuallyreach the egg in the ovule?a) stigma, style, ovary, ovuleb) stigma, ovary, ovule, stylec) style, stigma, ovary, ovulead) ovary, ovule, stigma, stylee) ovule, ovary, style, stigma2. Which of the following is NOT part of a seed produced by a flowering plant?a) Embryob) Endospermc) seed coatd) Ovary3. Which one of the following protects seeds and sometimes aids in the dispersal ofseeds?a) Stemsb) Petalsc) Fruitsd) Stamense) Pistils4. Which of the following provides nutrient molecules for the growing embryo?a) cotlCotyleedons and endospermb) epicotyl and hypocotylsc) Radicald) Ovarye) Pistil197

5. Upon germination, the ______ of an embryo will give rise to the leaves.a) Hypocotylsb) Epicotylsc) Cotyledond) Endosperm6. Microspores are produced in the ______ .a) Stigmab) StOOvulec) Filamentd) Antherse) Ovary7. The structure of a pollen grain does NOT vary between flowers of differentplant species.a) Trueb) False8. Which of the following is the correct sequence in life cycle of a plant?a) fertilization, pollination, germinationb) fertilization, germination, pollinationc) pollination, germination, fertilizationd) pollination, fertilization, germination9. Pollinators help bring the sperm and egg cell together in flowering plants so thatgrowth can occur.a) Trueb) False198

10. After fertilization, the fertilized ______ becomes the seed and the ______ becomesthe fruit of the plant.a) ovule, ovaryb) ovary, ovulec) stamen, pistild) pistil, stamen11. Following fertilization, the zygote develops into an embryo located within aseed.a) Trueb) False12. To a botanist, peas and beans are classified as fruits and not as vegetables.a) Trueb) False13. Plants that have one cotyledon are called monocots.a) Trueb) False14. Strawberry plants can reproduce asexually through ______ .a) Stolonsb) Rhizomesc) "eyes"15. Flowering plants can reproduce only sexually.a) Trueb) False16. In both vegetative propagation and sexual reproduction in flowering plants, theparent and the newly produced plants have identical genes.a) Trueb) False199

Activity-9AHuman Male reproductive systemLearning outcome: Students will be able to identify the structure and function ofreproductive organs in human male.Content: The organs of the human male reproductive system are specialized for thefollowing functions:To produce, maintain and transport sperm (the male reproductive cells) andprotective fluid (semen)To discharge sperm within the female reproductive tractTo produce and secrete male sex hormonesUnlike the female, whose sex organs are located entirely within the pelvis, the male hasreproductive organs, or genitals, that are both inside and outside the pelvis. The malegenitals include:the testiclesthe duct system, which is made up of the epididymis and the vas deferensthe accessory glands, which include the seminal vesicles and prostate glandthe penisIn a guy who has reached sexual maturity, the two testicles, or testes, produce and storemillions of tiny sperm cells. The testicles are oval-shaped and grow to be about 2 inches(5 centimeters) in length and 1 inch (3 centimeters) in diameter. The testicles are alsopart of the endocrine system because they produce hormones, including testosterone.Testosterone is a major part of puberty in boys, and as a guy makes his way throughpuberty, his testicles produce more and more of it. Testosterone is the hormone that200

causes boys to develop deeper voices, bigger muscles, and body and facial hair, and italso stimulates the production of sperm.Alongside the testicles are the epididymis and the vas deferens, which make up theduct system of the male reproductive organs. The vas deferens is a muscular tube thatpasses upward alongside the testicles and transports the sperm-containing fluid calledsemen. The epididymis is a set of coiled tubes (one for each testicle) that connects to thevas deferens.The epididymis and the testicles hang in a pouch-like structure outside the pelvis calledthe scrotum. This bag of skin helps to regulate the temperature of testicles, which needto be kept cooler than body temperature to produce sperm. The scrotum changes size tomaintain the right temperature. When the body is cold, the scrotum shrinks andbecomes tighter to hold in body heat. When it's warm, the scrotum becomes larger andmore floppy to get rid of extra heat. This happens without a guy ever having to thinkabout it. The brain and the nervous system give the scrotum the cue to change size.The accessory glands, including the seminal vesicles and the prostate gland, providefluids that lubricate the duct system and nourish the sperm. The seminal vesicles aresac-like structures attached to the vas deferens to the side of the bladder. The prostategland, which produces some of the parts of semen, surrounds the ejaculatory ducts atthe base of the urethra, just below the bladder. The urethra is the channel that carriesthe semen to the outside of the body through the penis. The urethra is also part of theurinary system because it is also the channel through which urine passes as it leaves thebladder and exits the body.The penis is actually made up of two parts: the shaft and the glans. The shaft is the mainpart of the penis and the glans is the tip (sometimes called the head). At the end of theglans is a small slit or opening, which is where semen and urine exit the body through201

the urethra. The inside of the penis is made of a spongy tissue that can expand andcontract.Activity: The teacher would discuss the changes that take place in the males andfemales at the age identified with puberty.1. Each group is given two diagrams, one is labelled the other is blank2. The students will quiz each other on the male reproductive system until theycan label each organ on the diagram.3. They should take turns quizzing partner A first and B second4. The students can also be given a word search with male reproductivevocabulary to help strengthen the students understanding of the material.Activity 9BHuman Female reproductive systemLearning outcome: Students will be able to understand the structure and function offemale reproductive organ.1. Use transparencies and powerpoint slides show and explain different parts ofthe female reproductive organs. The students will trace the journey of the eggfrom the ovaries.202

2. The students will view a video on puberty and discuss its contents.3. The class will review, on the chalkboard, those changes that occur in thefemale.Content:The external part of the female reproductive organs is called the vulva, which meanscovering. Located between the legs, the vulva covers the opening to the vagina andother reproductive organs located inside the body.The fleshy area located just above the top of the vaginal opening is called the monspubis ). Two pairs of skin flaps called the labia surround the vaginal opening.The clitoris a small sensory organ, is located toward the front of the vulva where thefolds of the labia join. Between the labia are openings to the urethra (the canal thatcarries urine from the bladder to the outside of the bodyand vagina. Once girls becomesexually mature, the outer labia and the mons pubis are covered by pubic hair.A female's internal reproductive organs are the vagina, uterus, fallopian tubes, andovaries.The vagina is a muscular, hollow tube that extends from the vaginal opening to theuterus. The vagina is about 3 to 5 inches (8 to 12 centimeters) long in a grown woman.Because it has muscular walls it can expand and contract. This ability to become wideror narrower allows the vagina to accommodate something as slim as a tampon and aswide as a baby. The vagina's muscular walls are lined with mucous membranes, whichkeep it protected and moist. The vagina has several functions: for sexual intercourse, asthe pathway that a baby takes out of a woman's body during childbirth, and as theroute for the menstrual blood (the period) to leave the body from the uterus.A thin sheet of tissue with one or more holes in it called the hymen partially covers theopening of the vagina. Hymens are often different from person to person. Most women203

find their hymens have stretched or torn after their first sexual experience, and thehymen may bleed a little (this usually causes little, if any, pain). Some women who havehad sex don't have much of a change in their hymens, though.The vagina connects with the uterus, or womb, at the cervix. The cervix has strong,thick walls. The opening of the cervix is very small (no wider than a straw), which iswhy a tampon can never get lost inside a girl's body. During childbirth, the cervix canexpand to allow a baby to pass.The uterus is shaped like an upside-down pear, with a thick lining and muscular walls— in fact, the uterus contains some of the strongest muscles in the female body. Thesemuscles are able to expand and contract to accommodate a growing fetus and then helppush the baby out during labor. When a woman isn't pregnant, the uterus is only about3 inches (7.5 centimeters) long and 2 inches (5 centimeters) wide.At the upper corners of the uterus, the fallopian tubes connect the uterus tothe ovariesThe ovaries are two oval-shaped organs that lie to the upper right and left ofthe uterus. They produce, store, and release eggs into the fallopian tubes in the processcalled ovulation.Each ovary measures about 1½ to 2 inches (4 to 5 centimeters) in agrown woman.There are two fallopian tubes, each attached to a side of the uterus. The fallopian tubesare about 4 inches (10 centimeters) long and about as wide as a piece of spaghetti.Within each tube is a tiny passageway no wider than a sewing needle. At the other endof each fallopian tube is a fringed area that looks like a funnel. This fringed area wrapsaround the ovary but doesn't completely attach to it. When an egg pops out of an ovary,it enters the fallopian tube. Once the egg is in the fallopian tube, tiny hairs in the tube'slining help push it down the narrow passageway toward the uterus.The ovaries are also part of the endocrine system because they produce female sexhormones such as estrogen and progesterone.204

Following vocabulary should be discussed in detail as given below-Vagina – is a muscular passageway that extends from the uterus to the outside ofthe body.Ovaries - are the female sex glands that produce ova and hormones.Ovulation - is the process of releasing one mature ovum each month.Fallopian tubes - are tubes that draw the ovum in.Zygote - is the union of the sperm and the ovum.Uterus - is a muscular organ about the size of a fist.The students are expected to label the parts of female reproductive system andhighlight the role of each part.205

Worksheet 9AMatch the functions of male and female parts correctly.Worksheet 9BQUESTION 1:Which part of the female reproductive system contains thousands of egg cells?OvariesUterusVagina206

QUESTION 2:Where does a baby (fetus) grow and develop inside of the mother?StomachUterusFallopian tubeQUESTION 3:Where does fertilization take place? Where will the father's sperm cell find and fertilizean egg cell inside of the mother's body?QUESTION 4:What is it called when the lining of the uterus breaks down and slowly flows from thevagina over a period of 3 to 8 days?OvulationMenstruationFertilizationQUESTION 5:What is the tube shaped passage that connects the uterus with the outside of the body?CervixFallopian tubeVagina207

Worksheet-9CFemale AnatomyFill in the Blank: Using the word bank below put the word that best corresponds withthe definition in the blank beside the definition.Word Bank: Uterine horns, Ovaries, Yellow Body, Oviducts, Uterus, Cervix, Vagina,Vulva1. _____________ This produces progesterone which is the hormone of pregnancy.2. _____________ The place were the embryo develops.3. _____________ An organ that has a lot of connective tissue. It is the passagebetween the uterus and the vagina.4. _____________ The place where the embryo attaches and develops in most species.5. _____________ They produce ova and the female sex hormones.6. _____________ This is the exterior part that leads to the vagina.7. _____________ This serves as the female organ of copulation and the birth canal.8. _____________The place where sperm and egg meet and fertilization takes place.208

Activity -10(Fertilization)Learning outcome- The students will be able to describe the process of reproductionand development including fertilization.Content- The gametes, both containing half the genetic information needed to producethe offspring, fuse together, meaning all the genetic information required for theoffspring to grow is present. For this to occur, sexual intercourse must occur in order forthe semen (sperm) to be ejaculated and have the potential to fuse with the ovum.Millions of sperm are released at the point of ejaculation, and when ejected, they 'swim'towards the female egg with their thread-like tail. This race towards the egg is fuelledby a fuel tank of ATP that provides the energy for their efforts.After a long journey, many of the sperm will have died out in their efforts to reach theegg, though some still have to the potential to fertilise it. Each will attach itself to theovum but only one should succeed in penetrating it. Enzymes contained in the acrosome(head) of the sperm break down the wall of the egg. When fertilised, the egg secretesvarious hormones to prevent it from being overwhelmed by the other millions of spermattempting to fertilise it.The ZygoteWithin hours of conception the fused gametes, a zygote, undergoes cell division. Thepresence of a hormone called progesterone prevents further female eggs beingproduced. Within the first week after conception the fertilised egg travels towards theuterus, where the continued growth of the zygote will occur in the form of an embryo.Activity-The teacher would arrange for (Fertilization kit) - 1 big gum ball, 1 skittle, 1 gummyworm, 1 piece of licorice, and 1 doughnut already divided out into kits.209

The teacher may explainThe gumball is an ovary, the skittle is an egg, the gummy worm is a sperm, the licoriceis a fallopian tube, and the doughnut is the uterus. Set the ovary to the left side. Placethe licorice facing diagonally down towards the right. Finally place the doughnut onthe other end of the licorice. This is the reproductive tract. The students would tellwhat each piece of food represents.Process of FertilizationPlace the egg up by the ovary. Place the sperm down by the uterus. The ovary needs torelease the egg and have it float down (beside the fallopian tube). The sperm needs toswim through the uterus and up the fallopian tube. The sperm and egg then unite inthe fallopian tube and both need to float down to the uterus and attach themselves tothe inside of the uterus for further development of the embryo and later fetus.I. Stages of Prenatal Development1. Fertilization – When the sperm and egg unite. When fertilization occurs, celldivision occurs. It starts with 2, 4, 6, and 8 and so on.2. Attachment – The embryo that has gone through much cell division attachesitself to the uterus for further development.3. Embryonic Stage – The period when body parts and organs start to form. Thelength of time differs between species4. Fetal Period – Period that lasts until birth is mainly a time when body parts andorgans mature.210

Worksheet -101. The union of sperm and egg is calledA. ParturitionB. FertilizationC. Gestation2. The process of giving birth is calledA. ParturitionB. FertilizationC. Gestation3. The length of time a fetus matures is calledA. ParturitionB. FertilizationC. Gestation211

4. Describe how fertilization happens in the female reproductive tract in detail.5. Describe normal presentation of a foal.6. Name three abnormal birth presentations.Activity -11Family planningLearning Outcome- The students will understand the need for family planning andvarious ways to conduct the same.Content: Family planning helps to prevent conception and reduce the risk ofpregnancy. The biggest advantage of family planning tools is that they save from thehassles of pregnancy termination and abortion.Family planning tools or types of family planning are broadly categorized into twosections: Natural Family Planning Methods and Artificial Family Planning Methods.Natural Family PlanningNatural family planning is based on avoiding sexual intercourse during the fertileperiod of women.Artificial Family PlanningArtificial family planning signifies various contraception methods that includehormonal methods like birth control pills and Norplant implant, barrier methods like212

condoms which act as foremost male contraception, cervical caps and diaphragms, andsterilization or permanent contraception. Another popular hormonal birth controlmethod is the IUD (Intrauterine device). This is a small metal device which is insertedinside the uterus of \the female of reproductive age. IUD prevents unwantedpregnancy and is an effective birth control device.Male Contraception MethodsContraceptives or protective measures for safer sex should be taken by both thepartners. There are certain specific contraceptive methods meant separately for malesand females.Activity-III.The students will prepare a skit to raise awareness for family planning andcommunicate the methods used. They may present the skit as a part of formativeassessmentThe students will carry out a signature campaign to reach out to localcommunity regarding the family control methodsWorksheet -11Match the following correctly-Male Contraception methodsAbstinenceCondomsPrevents sperms from moving- Latex cover for penis.- Pulling the penis out of vagina just at the time of ejaculation.Surgically, blocking the tubes carrying sperm.SpermicideAvoiding the indulgence in any kind of sex act.213

Female Contraception MethodsResearch and complete the following :Birth Control ImplantA thin matchstick like implant inserted in the ____________to prevent the formation ofeggs.Birth Control Patch- A thin plastic path stuck on the skin to keep the ___________ from releasing the eggs.Birth Control Pills- Pills taken on a daily basis to avoid ______________.Birth Control Shot- An ____________that prevents pregnancy.Birth Control Sponge- A soft, round sponge inserted deep in the ______________ to avoid pregnancy.Birth Control Vaginal Ring- A flexible ring inserted into a woman's vagina so as to keep the ovaries from releasing_________________Breastfeeding- When a female breastfeeds her baby, the body automatically stops forming_________________necessary for getting pregnant.Cervical Cap- Cervical cap refers to a silicon cup, that is inserted into the vagina to cover cervix. Itblocks the opening to the ____________and also stops the sperms from moving.214

Diaphragm- Diaphragm is similar to cervical cap. It is a latex cup inserted into the vagina to covercervix so as to block uterus as well as prevent ___________ from moving.Sterilization- Sterilization can be done in a number of ways. It basically involves blocking the_______________ to prevent pregnancy temporarily or permanently as per the choice.IUD- Intrauterine device or IUD is a 'T' shaped device inserted in the ____________ toprevent pregnancy.Activity -12Sexually transmitted diseaseLearning Outcome- The students will become aware of the sexually transmitteddiseases and learn how can they be prevented.Content- Sexually transmitted diseases (STDs, venereal diseases) are among the mostcommon infectious diseases in the United States today. STDs are sometimes referred toas sexually transmitted infections, since these conditions involve the transmission of aninfectious organism between sex partners. More than 20 different STDs have beenidentified, and about 19 million men and women are infected each year in the UnitedStates, according to the CDC (2010).Depending on the disease, the infection can be spread through any type of sexualactivity involving the sex organs, the anus, or the mouth; an infection can also be spreadthrough contact with blood during sexual activity. STDs are infrequently transmitted byany other type of contact (blood, body fluids or tissue removed from an STD infectedperson and placed in contact with an uninfected person); however, people that share215

unsterilized needles markedly increase the chance to pass many diseases, includingSTD's (especially hepatitis B), to others. Some diseases are not considered to be officiallyan STD (for example, hepatitis types A, C, E) but are infrequently noted to betransferred during sexual activity. Consequently, some authors include them as STD's,others do not. Consequently, lists of STD's can vary, depending on whether the STD isusually transmitted by sexual contact or only infrequently transmitted.Student ActivityThe students may be divided into groups of three or four to work on a single brochure.Urge students to be creative in developing the brochures and to use computer graphicsprograms to make brochure . The brochures should be brief and easy to read, but alsoinformational. They should coverwhat STDs are and how they are transmitted,descriptions of some of the most common STDs (including HIV/AIDS) and whythey are dangerous,how STDs are treated, andwhat to do to prevent transmission of STDs.1. The students need to work in groups of three or four. They will be given a set ofcards by the teacher each with different information. Some of the cards give namesof STD‘s, others give information about symptoms, prevention, treatment and otheraction that can be taken.2. The groups are expected to categorise the information. They should record thenumbers of cards grouped together and the reason why they have put them into acategory.3. The students read out the numbers to the class who try to guess the reason theyhave been grouped together.4. The groups then decide on 5 hypotheses about STD‘s.216

Following the activity, the students may answer the following questions-- How are STD‘s caught?- How might some one know that he/she might have got STD?- How can an individual protect him/herself against STD‘s?- What steps can a person infected with STD take?The students will be given the following cards and will have to match them correctly1. Chlymadia 2. Tell your partner3. Go to your family doctor 4. HIV5. Phone a help line like theNational AID‘s helpline6. Know how to use a condom7. Blood test 8. Full examination217

9. Wait to have sex 10. Herpes12. Damage to fallopian tubes – this11. Pain when you go to the toiletcan make it difficult for a womanto have a baby later on14. Go to an NHS sexual health13. Genital wartsclinic15. (GUM)16. Do not have sex again until youare well17. Gonorrhoea18. Inflammation of joints and eyes 19. Needing to pass urine more often20. Urine samples tested 21. HIV test218

22. Insist in wearing a condom 23. Inflammation of the testes24. Itching, rash, sores or pain nearin the genital area25. Unable to fight infections26. Pain in pelvic area throughoutlife (for women)27. An unusual discharge fromgenitalsResource- www.nottinghamshire.gov.uk/stdslessonWorksheet -12Sexually transmitted diseases, or STDs, are infections that can be transferred from oneperson to another through sexual contact and also by contact with infected blood orsecretions. Most STDs are curable if diagnosed and treated in their early stages, butsome of them are quite dangerous that they can even cause death. Some can also lead torelated conditions such as pelvic inflammatory disease, cervical cancer, andcomplications in pregnancy. Most STDs can be avoided by practising safe sex byrespecting the relationship and limiting the partners.219

AIDSCrabsGonorrheaSyphilisChlamydiaGenital WartsGenital HerpesNon-Specific UrethritisFor each of the Sexually Transmitted disease given above write the following:Symptoms- (in male)Symptoms- (in Female)Adverse effectsTestTreatmentActivity 13Safe sex vs HIV/AIDSLearning Outcome: Students will be able to:Identify some of the sensitive issues connected with preventing, acquiring, andcoping with HIV/AIDS220

Examine personal knowledge in terms of what they already know and what theywant to know. Consider how HIV/AIDS affects many more people than it infects .Content-AIDS is caused by HIV.HIV is a virus that gradually attacks immune system cells. As HIV progressivelydamages these cells, the body becomes more vulnerable to infections, which it will havedifficulty in fighting off. It is at the point of very advanced HIV infection that a personis said to have AIDS. It can be years before HIV has damaged the immune systemenough for AIDS to develop.A person is diagnosed with AIDS when they have developed an AIDS related conditionor symptom, called an opportunistic infection, or an AIDS related cancer. Theinfections are called ‗opportunistic‘ because they take advantage of the opportunityoffered by a weakened immune system.It is possible for someone to be diagnosed with AIDS even if they have not developedan opportunistic infection. AIDS can be diagnosed when the number of immune systemcells (CD4 cells) in the blood of an HIV positive person drops below a certain level.Antiretroviral treatment can prolong the time between HIV infection and the onset ofAIDS. Modern combination therapy is highly effective and someone with HIV who istaking treatment could live for the rest of their life without developing AIDS.An AIDS diagnosis does not necessarily equate to a death sentence. Many people canstill benefit from starting antiretroviral therapy even once they have developed anAIDS defining illness. Better treatment and prevention for opportunistic infections havealso helped to improve the quality and length of life for those diagnosed with AIDS.221

Treating some opportunistic infections is easier than others. Infections such as herpeszoster and candidiasis of the mouth, throat or vagina, can be managed effectively inmost environments. On the other hand, more complex infections such as toxoplasmosis,need advanced medical equipment and infrastructure, which are lacking in manyresource-poor areas.It is also important that treatment is provided for AIDS related pain, which isexperienced by almost all people in the very advanced stages of HIV infection.ActivityAsk students to share what they know about HIV: How does it get transmitted? Whathappens to the body once someone contracts the virus? What groups are most at risk?After a brief discussion, share the following facts with students about HIV/AIDS. Makesure that students understand the difference between HIV and AIDS. HIV (humanimmunodeficiency virus) is a virus that severely damages the immune system byinfecting and destroying certain white blood cells. AIDS (acquired immunodeficiencysyndrome) is the final, life-threatening stage of infection of HIVAsk students to share what they know about contracting HIV, the virus that causesAIDS. Review the different ways that HIV is transmitted:Unprotected sexual contact with an infected personTransmission from an infected woman to her fetus or babyThrough needle sharing among intravenous drug usersRarely, through accidents involving needle-stick injuries and other bloodexposures of healthcare providers (Healthcare workers now wear gloves,masks, and other protective clothing during many examinations andprocedures.)Now talk about ways that people can avoid getting and spreading AIDS. Examples:222

Avoid sexual contact with anyone who is or might be infected with HIV, orabstain from sexual contact.Practice protected sex with a person who is infected with HIV or whose infectionstatus is unknown.Drug users should seek help to stop taking drugs and should never sharehypodermic needles, syringes, or other injection equipment.Women may take AZT during pregnancy and avoid breastfeeding to reduce therisk of transmitting HIV to the fetus or baby.If you have put yourself in a high-risk situation, get tested for HIV to avoidspreading it to othersStudents will design and implement an action plan to support a peer who is talking toparents/ caregivers about HIV/AIDS and its impact on families.Students will decide how to support a friend as he or she talks to parents/caregiversabout HIV/AIDS and its impact on families.Divide students into pairs or small groups and have each pair choose one of thepopulations you have listed to learn more about its risk for getting HIV/AIDS. Theywill find more statistics, background, and prevention resources for each population atWho Gets AIDS?. As students research a population, have them consider the followingquestions:What are the specific dangers for this population?How has the risk of contracting HIV/AIDS changed for this populationover the past several years? (Provide statistics when possible.)What behaviors put this population at risk for HIV/AIDS?How could members of this population change their behavior to avoidgetting or spreading HIV/AIDS?223

Finally, ask each pair to create a public awareness campaign for that audience.Encourage them to be creative and consider the tone, language, and medium thatwould be most appropriate for that audience. For example, they may create a publicservice announcement for teens, a brochure for obstetrics offices, a needle exchangeprogram for public health clinics, a poster for clubs frequented by homosexual men, aWeb page for young professional men and women, or a bulletin board for their schoolhallway.Worksheet 13Do you think most young people consider themselves at risk for HIV/AIDS? Whyor why not? As a result of this lesson, how has your view of AIDS changed?Given that young people are contracting HIV at alarming rates, why do you think somany are reluctant to abstain from sex or use condoms? What is it about beingchaste or using condoms that is "uncool"? Do you think boys and girls view thisissue differently? If so, why? Is there a difference among ethnic groups?Imagine you have a friend who practices unsafe sex or is an injection drug user.What would you say to encourage him or her to stop or change this behavior?224

Explain how injection drug use directly endangers those who don't use drugs.Activity 14Child bearing and woman‘s healthLearning outcome- students will be able to explain the adverse effects of birth controlon the female anatomy. They would become sensitive for the women‘s health.Content-Considering the population explosion, increasing inflation and scarcity of resources, thefamily trends have shifted to nuclear families with number of children limited to one ortwo. Family planning refers to the natural and artificial birth control methods that allowyou to control the size of your family and the gap between your children.Advantages of Family PlanningFamily planning helps you prevent conception and reduce the risk of pregnancy. Thebiggest advantage of family planning tools is that they save you from the hassles ofpregnancy termination and abortion. Adopting a family plan directly effects a woman'shealth in a good way by preventing unwanted and unplanned pregnancies andsubsequent abortions. Restricting the family size allows more resources for bringing upyour children and sustaining a family in a balanced way. Adopting family planningmethods helps couples to let their children have a more focused upbringing, bettereducation and other amenitiesActivity-The students will be able to define terms associated with changes that occur inthe female. The class will be able to trace the passage of the egg cell during225

fertilization and non-fertilization. Student will be aware and understand thosephysical changes that occur during puberty.Students will define the various parts of the female anatomy.Students will label the parts of the female anatomy on the model and play birthcontrol trivia.The students may consider how being pregnant would affect the daily routines.Ask them to take about 10 minutes to highlight the activities in a typical day thatwould be impossible or would dramatically change if they were pregnant. Askthem to share their thoughts with the class. Not only might they detect time andfinancial restrictions, but they might also recognize physical limitations thatoccur during pregnancy that limit what activities they can do.Multicultural:Students from all ethnic groups will encounter or experience physical change.The changes will vary but the concept is the same for all ethnic groupsthroughout the universe.226

Rubrics of AssessmentParameterBeginningApproachingMeetingExceeding(1)(2)(3)(4)1 Is able tounderstandtheimportancerepoduction2 Discuss theimportanceof vegetativepropagation3 Try todistinguishbetweenasexual andsexualreproduction4 To relate tothe sexuallytransmitteddiseases withtheirpreventionandtreatment.5 Explain theprocesses offertilization.227

ResourcesActivity-1Activity-2Activity-3Activity-4Activity-5Activity-6Activity-7Need of ReproductionOffsprings resemble Parent/ParentsWww.Lessonsnips.comAsexual Reproductionims.ode.state.oh.us/ODE/IMS/Lessons/Content/CSC_LP_S02_BB_L06_I05_01.doc · DOC fileVegetative Reproduction in plants-Vegetative propagationhttp://www.lessonsnips.com/ ansc-04/Asexual and Sexual Reproductionhttp://wn ww.bookrags.com/research/reproduction-asexual-andsexual-Importance of sexual reproductionhttp://www.glencoe.com/sec/science/voyages/voyagesgreen/unit6/chapter16/svna7n16-2.pdfSexual Reproductin in plants-IThe Structure and Functions of Flowershttp://leavingbio.net/TheStructureandFunctionsofFlowers%5B1%5D.htmAudio-visual activityhttp://www.powershow.com/view/19f6d-Mzc3M/Flower_Dissection_ActivityActivity-8 Sexual Reproductin in plants-IIPollination and Fertilizationhttp://leavingbio.net/TheStructureandFunctionsofFlowers%5B1%5D.htAudio-Video Activityhttp://www.youtube.com/watch?v=X7uH46X0G5YActivity-9A Male reproductive system228

http://kidshealth.org/parent/general/body_basics/male_reproductive.html#Activity-9B Female Reproductive systemhttp://kidshealth.org/teen/sexual_health/changing_body/female_repro.html#Activity-10 Fertilizationhttp://www.biology-online.org/7/1_fertilisation.htmActivity-11 Family Planninghttp://health.indiamart.com/familyplanning/Activity-12 Sexually transmitted diseaseshttp://www.emedicinehealth.com/sexually_transmitted_diseases/article_em.htmhttps://sites.google.com/site/samsuesz/home/webquest/teacherActivity-13 AIDShttp://www.avert.org/aids.htm229

CENTRAL BOARD OF SECONDARY EDUCATIONShiksha Kendra, 2, Community Centre, Preet Vihar,Delhi-110 092 India